Humans are social creatures, and as such, our relationships are crucial to our health and wellbeing. However, our relationships are always in flux. Let’s face it: none of us are perfect, which means that people disagree, make mistakes, and miscommunicate, which cultivates tension and negative feelings.

This is where forgiveness comes in. Sometimes, it can be extremely difficult to reach a point where you can forgive someone. Not going through the process of forgiveness may feel easier at the moment, but it will take a very real toll on your health, both physically and mentally.

Everett L. Worthington Jr., Ph.D., is a professor at Virginia Commonwealth University in Richmond. His psychology research specializes in forgiveness and how people reach a state of true forgiveness. According to his work, how people eventually become ready to forgive varies, however, they usually fall under two categories: decisional forgiveness and emotional forgiveness.

“You can experience a change in your emotion, and then decide to forgive,” Dr. Worthington explains. “Or you can decide to forgive first and experience those changes emotionally later on.”

If you have been struggling to forgive someone in your life (or even yourself), and need a push in the right direction, then here are three evidence-backed ways that forgiveness affects your health.

Forgiveness helps you manage stress

Past research shows that anger, hostility, and stress are the feelings you harbor by not being able to forgive.

This 2016 study published in Annals of Behavioral Medicine revealed that people who were able to forgive perceived a decrease in their stress, which led to a decrease in psychological distress.

“Although forgiveness is not the only strategy available for coping with adversity, according to this model of forgiveness, it is one of the more effective responses for reducing stress perceptions and enhancing health,” the study authors write.

On the other hand, the presence of the stress hormone cortisol negatively affects our bodies in a variety of ways. For instance, chronically elevated cortisol is known to shrink the size of parts of your brain including the hippocampus, which is the portion of the brain that turns experiences into memories.

According to Worthington, this could mean that not being able to forgive and let go of grudges could potentially affect memory. In a 2018 study published in Neurology, researchers investigated how blood cortisol levels affected memory in more than 2,200 healthy middle-aged people. They found that people with high blood cortisol levels over time, particularly women, had poorer memory and performed worse on cognitive tests. They also seemed to have less gray matter in other parts of the brain.

Forgiveness is great for heart health

Forgiveness activates the parasympathetic nervous system, which slows breathing and heart rate and increases digestion. It’s known as the “rest and digest” response—the opposite of the “fight-or-flight” response.

The sympathetic and the parasympathetic nervous systems work in tandem, allowing your body to function normally and regulate things like blood pressure and heart rate. However, if a person is under chronic stress, (which may happen if someone is holding on to anger) then the body may remain in the fight-or-flight response for too long.

To prevent this from happening, people must try to activate the parasympathetic nervous system to calm themselves, and this includes practicing forgiveness. This could affect long-term health outcomes, like cardiovascular function, and may even be a predictor of mortality according to a study published in the Journal of Behavioral Medicine, that found that forgiving others is associated with a decreased risk for all-cause mortality.

Forgiveness helps you ruminate less

Refusing to forgive breeds rumination, which means playing something over and over in the mind. “We all ruminate,” Worthington says, “but the way that we ruminate is kind of individual. Some people do it angrily, some people ruminate hopelessly or feel depressed.” If rumination becomes a constant habit, it can lead to psychological disorders.

These repetitive thoughts can eventually lead to anger disorders, obsessive-compulsive disorder, post-traumatic stress disorder, anxiety, depression, or psychosomatic disorders, which is when stress or anxiety manifests themselves physically as stomach pain or migraines.

People who forgive will likely still ruminate, however they will be able to let go of the bitterness and anger that goes with it, effectively reducing its toxic effects on their mental and physical health.