The Cost of Not Forgiving: How Resentment Affects Your Health
What Unforgiveness May Be Costing You Physically, Mentally and Emotionally
There is a price we sometimes pay for the things that happened to us long after the person who hurt us has disappeared from our lives.
The argument is over. The relationship has ended. The betrayal happened years ago. The words were spoken and cannot be unsaid. The person may not even remember what they did.
And yet, somehow, they can still occupy precious space in our minds.
We replay the conversation. We imagine what we should have said. We wonder how someone could have treated us that way. We feel the injustice all over again. Sometimes we tell ourselves that we will never forgive them because forgiving would somehow mean that what happened was acceptable.
But there is an important distinction: Forgiveness does not mean saying that what happened was okay. It does not mean forgetting. It does not mean trusting someone again. And it certainly does not mean allowing someone who harmed you back into your life.
Forgiveness can simply mean deciding that you no longer want to carry the emotional weight of what happened. And that raises an interesting question:
What is the cost of not forgiving?
Increasing scientific research suggests that holding on to anger, resentment, hostility and repetitive thoughts about past offences may have consequences for our psychological wellbeing, sleep and even aspects of physical health. The fascinating thing is that the person who wronged you may have moved on. But your nervous system may still be paying the bill.
When the past keeps happening in your mind
One of the greatest costs of unresolved hurt is rumination. Rumination is the tendency to repeatedly think about an upsetting event, turning it over in your mind again and again.
"Why did they do that?"
"How could they treat me like that?"
"I should have said..."
"If only I had..."
"They got away with it."
The event may have happened once. But every time we mentally revisit it, we can experience another emotional echo of the event.
Research examining rumination and forgiveness has found that increases in rumination about interpersonal offences are associated with decreases in forgiveness, with anger appearing to play an important role in this relationship. (PubMed) This creates a potentially exhausting cycle:
hurt → anger → rumination → emotional distress → more rumination.
And the danger is that the original event gradually becomes only part of the problem. The other part is what our mind continues to do with it.
The mental cost: when resentment takes up valuable mental space
Our minds have limited attention. Every hour spent mentally arguing with someone who is not even present is an hour that cannot be spent fully experiencing the life that is happening now. That doesn't mean you can simply decide not to think about something painful. Significant hurt often needs to be acknowledged, processed and understood.
But there is a difference between processing pain and perpetually rehearsing it. Research has repeatedly connected forgiveness with better psychological wellbeing. A systematic review and meta-analysis of forgiveness interventions found that forgiveness-focused interventions were associated with reductions in depression, anger, hostility, stress and distress, while also increasing positive affect. (PubMed)
Another large meta-analysis examined 103 independent samples involving more than 26,000 participants. Overall, forgiveness was reliably associated with health outcomes, with the relationship particularly strong for psychological health. The researchers also found robust associations with cardiovascular indicators such as heart rate and blood pressure. (PubMed)
This does not mean that unforgiveness automatically causes depression or heart disease. That distinction is important. Most research in this area demonstrates associations rather than proving that resentment directly causes a particular illness. But the evidence does suggest that how we respond psychologically to interpersonal hurt matters. And that gives us something worth considering:
Perhaps forgiveness is not primarily something we do for the person who hurt us. Perhaps it is something we do to free ourselves.
The emotional cost: carrying anger long after the event
Anger is not inherently bad. In fact, anger can be useful. It can tell us that a boundary has been crossed. It can motivate us to protect ourselves. It can give us the courage to leave an unhealthy relationship or speak up when something is wrong.
The problem begins when anger becomes a permanent resident. When the original situation has ended but the emotional response remains permanently switched on, we may find ourselves repeatedly experiencing frustration, bitterness, resentment or hostility.
Forgiveness research offers an interesting alternative. A meta-analysis of psychotherapeutic forgiveness interventions found that forgiveness treatments produced significant improvements in forgiveness and also changes in depression, anxiety and hope. (PubMed)
In other words, learning to forgive isn't simply about becoming a "nicer" person. It may be part of learning how to regulate what happens inside us after we have been hurt.
The physical cost: your body listens to your thoughts
Perhaps one of the most compelling reasons to reconsider long-term resentment is that emotional experiences don't remain entirely in the mind. They are accompanied by physiological responses. Stress, anger and emotional arousal can influence heart rate, blood pressure and other bodily processes.
The research connecting forgiveness and physical health is still developing, but the evidence is intriguing. The large meta-analysis of 26,043 participants mentioned earlier found associations between forgiveness and several physical health indicators, including blood pressure, heart rate, cortisol and bodily pain. The researchers concluded that forgiveness may have implications for cardiovascular stress, while also stressing that the psychological associations were stronger than the physical ones. (PubMed)
Research involving 85 patients with coronary artery disease found that greater forgiveness was associated with lower anxiety, depression and perceived stress, as well as more favourable cholesterol ratios. The authors suggested that forgiveness may be associated with reduced cardiovascular risk, although this type of observational research cannot establish cause and effect. (PubMed)
The message isn't: "Forgive someone and you won't get sick." That would be an irresponsible interpretation of the science. The more reasonable message is: Our emotional relationship with stressful experiences appears to be relevant to our overall wellbeing, and forgiveness may be one way of reducing some of the psychological burden associated with unresolved interpersonal hurt.
The sleep cost: when your pillow becomes a courtroom
Have you ever noticed that difficult thoughts seem louder at night? During the day there are distractions. Work. Children. Shopping. Conversations. Emails. Television. Exercise. Other people's needs.
Then the lights go out. And suddenly, there it is. "I can't believe they did that."
Sleep and forgiveness have been investigated together, and the findings are particularly interesting. A nationally representative study of 1,423 American adults found that forgiveness of others was associated with sleep and with better self-reported health. Sleep itself was associated with health and partly mediated the relationship between forgiveness and health. (PubMed Central (PMC))
Another study found that negative affect and anger rumination helped explain the relationship between forgiveness and sleep quality. (PubMed)
And more recent experimental work compared rumination about an offence with a more compassionate form of reappraisal. Participants using compassionate reappraisal experienced less negative emotion and, compared with rumination, showed faster sleep onset, fewer sleep disturbances and fewer intrusive thoughts about the offence. (PubMed)
Think about that. The person who hurt you may be sleeping peacefully. Meanwhile, you may be lying awake at 2 a.m. reliving something that happened five, ten or twenty years ago.
That is a very high price to pay for someone else's behaviour.
The opportunity cost: what could you do with all that energy?
There is another cost that science cannot easily put a number on: the life you could be living instead. Imagine that resentment is a heavy suitcase. You carry it everywhere. To breakfast. To work. Into new relationships. On holiday. Into conversations. Into bed.
Sometimes you even carry it into relationships with people who had absolutely nothing to do with the original offence. And because you've been carrying it for so long, you may eventually forget that you have a choice about putting it down.
Forgiveness can be understood as releasing yourself from the responsibility of continually revisiting the offence.
Not forgetting.
Not approving.
Not excusing.
Releasing.
Forgiveness doesn't mean forgetting
The phrase "forgive and forget" can actually be problematic. Some experiences should be remembered. If someone repeatedly abused your trust, remembering what happened can help you establish healthier boundaries in the future. If someone harmed you, forgiveness does not require reconciliation.
You can forgive someone and still decide: "I don't want you in my life." You can forgive someone and still maintain boundaries. You can forgive someone and still seek justice. You can forgive someone and still acknowledge that what they did was wrong. And you don't have to forgive quickly.
Some wounds take time.
Some require therapy.
Some require grieving.
Some require anger before forgiveness is even possible.
The goal is not to suppress your emotions. The goal is to stop allowing the past to control your present.
Forgiveness is not the same as reconciliation
This distinction deserves emphasis. Forgiveness is an internal process. Reconciliation is a relationship process. You need another person's cooperation for reconciliation. You don't need it for forgiveness. You can forgive someone who has died. You can forgive someone who refuses to apologise. You can forgive someone who doesn't believe they did anything wrong. You can forgive someone you will never see again. And you can forgive while maintaining very firm boundaries.
In some situations, distance is healthy. Forgiveness doesn't require you to reopen a door that you wisely closed.
What happens when we stop feeding the story?
Imagine two people experiencing the same betrayal. Person A repeatedly revisits it:
"How could they do that?"
"They ruined everything."
"I'll never trust anyone again."
Person B acknowledges the pain:
"What happened hurt me deeply. It changed me. I didn't deserve it. But I don't want to spend the rest of my life carrying this person's actions."
Neither person is pretending that the betrayal didn't happen. But psychologically, they are relating to the event differently.
And research suggests that this difference matters. The 2022 study on compassionate reappraisal found that shifting away from offence-focused rumination toward compassionate reappraisal was associated with less anger and negative emotion, greater forgiveness and empathy, and better sleep-related outcomes. (PubMed)
Perhaps the question isn't: "How can I forget what they did?"
Perhaps it is: "How can I remember what happened without continuing to suffer from it?"
That is a very different question.
The nervous system doesn't know that the event is over
When we repeatedly revisit a painful event, we can trigger emotional responses associated with remembering it. That is why an event from twenty years ago can suddenly make your heart race, your stomach tighten or your jaw clench. The body responds to what the mind is experiencing in the present moment. This is one reason practices that reduce rumination and promote emotional regulation may be useful.
Mindfulness, compassionate reappraisal, journaling, therapy, meditation, movement and spending time in nature can all provide ways of stepping outside the repetitive mental loop.
They don't erase the past.
They change our relationship with it.
So, what is unforgiveness costing you?
Perhaps the better question isn't: "Do they deserve my forgiveness?"
Perhaps it is: "Do I deserve to be free?"
Free from the endless mental conversations.
Free from replaying the betrayal.
Free from carrying yesterday's anger into today's relationships.
Free from allowing somebody else's worst behaviour to occupy the best years of your life.
Free to sleep.
Free to laugh.
Free to trust yourself again.
Free to create something new.
The scientific literature certainly does not suggest that forgiveness is a magical cure-all. Nor does it prove that unforgiveness directly causes specific physical illnesses. But the evidence does provide a compelling picture: forgiveness is associated with better psychological wellbeing, less anger and stress, healthier emotional functioning and, potentially, better sleep and aspects of physical health. (PubMed)
And perhaps that is enough reason to explore it.
A gentle way to begin letting go
You don't have to wake up tomorrow and declare: "I forgive everyone!"
Instead, start somewhere smaller. Take one person who still occupies too much space in your mind. Write their name. Then write: What happened?
Tell the truth. Don't minimise it. Don't make excuses for them.
Then ask: What did this experience cost me?
Perhaps it cost you trust.
Perhaps confidence.
Perhaps years of anger.
Perhaps a relationship.
Perhaps sleep.
Perhaps your ability to believe that people could be good.
Then ask the most important question: What is it costing me now?
Finally, ask: What would I gain by putting some of this weight down?
You may not be ready to forgive. That's okay.
Perhaps you can simply become willing to heal. Perhaps forgiveness begins not with: "I forgive you." But with: "I no longer want what you did to have power over the rest of my life."
You don't have to carry someone else's behaviour forever
There is an extraordinary freedom in realising that the past cannot be changed — but your relationship with the past can change.
You cannot rewrite what happened.
You cannot make someone apologise.
You cannot force someone to understand the damage they caused.
You cannot travel backwards and protect the person you were then.
But you can begin to protect the person you are now. And perhaps forgiveness is one of the ways we do that. Not for them.
For you.
Because every day spent carrying resentment is a day of your life. Every night spent replaying an old argument is a night of your life. Every new relationship damaged by an old betrayal is part of the price. And eventually we have to ask ourselves: How much longer am I willing to pay?
Sometimes the most powerful thing we can say to the past is: "You happened. You mattered. You hurt me. But you do not get to own me anymore."
And then, slowly, gently, one breath at a time, we put the suitcase down.
A Final Thought on The Cost of Not Forgiving
"Forgiveness is not an occasional act; it is a constant attitude." — Martin Luther King Jr.
Perhaps forgiveness is not about giving someone else another chance. Perhaps it is about giving yourself another chance.
Another chance to sleep peacefully.
Another chance to love without the shadow of yesterday.
Another chance to laugh without remembering who tried to break you.
Another chance to walk forward without continually looking behind you.
And sometimes, the greatest gift you can give yourself is not forgetting what happened.
It is deciding that what happened next is going to be different.
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