Humans are really stubborn. If someone wrongs us, we're likely to hold a grudge with that person even after they have apologized.

Sure, staying mad at the person who made us feel miserable may seem like the righteous thing to do, but experts argue it's actually one of the most selfish and unhealthy things we can do in our lives.

So why do we still do it?

Holding onto a grudge validates our sense of injustice and suffering and confirms how right we are, according to licensed clinical social worker Nancy Colier, writing in Psychology Today:

"With our grudge intact, we know who we are: a person who was 'wronged.' As much as we don’t like it, there also exists a kind of rightness and strength in this identity. We have something that defines us — our anger and victimhood — which gives us a sense of solidness and purpose. We have definition and a grievance that carries weight."

As long as we have the identity as the one who was wronged, we feel entitled to empathy and special treatment from others. Letting go of our grudge means letting go of "whatever strength, solidity, or possible sympathy and understanding we receive through that 'wronged' identity," according to Colier.

You don't have to reconcile with the person who wronged you. But here are five reasons why you should forgive and let live.

1. Increased risk of chronic health problems

High levels of anger may increase the risk of coronary disease, according to a study by the American Heart Association. In addition, people who said they held grudges for years had an increased risk of multiple health problems, including heart disease, high blood pressure, stomach ulcers, back pain, and headaches, researchers at the Medical College of Georgia found.

2. It may be a lost cause anyway

We use grudges as a silent hint to the person who wronged us to come chase us down and apologize. But holding out like this may be a waste of time. It's important to distinguish if this person holds value in your life, according to Health's Leslie Barrie. If so, then be up front with the person and try to come to a resolution. If not, then it's better to move on.

3. You'll sleep better

People who remain angry about past verbal abuse, theft, deceit, and physical harm suffered sleep problems, according to a study reported by the Chicago Tribune. "Those who had forgiven the people who made them feel angry fell asleep faster, woke up less during the night, and were more alert during the day," the study found.

"Anger was designed to help us deal with short-term problems, not as a long-term solution that keeps you from functioning," Fred Luskin, director of the Stanford Forgiveness Project and author of "Forgive for Good," told the Tribune. "Long-term anger is really just a sign of fear. You're scared of something overwhelming you, and you don't feel comfortable seeking better options."

4. Releases feel-good hormones

It may seem like holding onto a grudge is a productive way to manage your sense of injustice, but it produces more negative emotions and stress. Harboring bitterness toward a person signals the stress response of the sympathetic nervous system, which raises the levels of cortisol, the body's stress hormone, according to Psychology Today.

On the flip side, resolving conflicts and letting go of your anger toward a person stimulates compounds in the body's parasympathetic nervous system, which increases human bonding and levels of the "love hormone" oxytocin — the same hormone that we experience during sexual pleasure.