It can kill you!

Researchers at Hope College found that simply IMAGINING getting revenge on someone raises your heart rate, constricts blood vessels, and causes other stress-related health problems. On the other hand, just TRYING to forgive someone lowers the level of stress hormones that damage your immune system. it’s a life-saving skill!

So here’s how to let go of grudges and get on with your life:

First: Don't wait for the other person to say “I’m sorry.” If you wait until someone apologizes before you forgive them, you’re placing control of how you feel in their hands. An apology may never come, but you can start feeling better right away by offering one yourself.
Next: Try to see the disagreement from the other person’s side.This can be hard. So, begin by looking at how you contributed to the problem. Then try writing yourself a letter from the other person’s point of view. This will help you empathize with them, making it easier to let go of blame.

And finally: Try to FORGIVE - not FORGET.Your hurt feelings won’t magically go away, and some offenses might require forgiving someone over and over again. So have patience.
Even if holding a grudge didn’t hurt your health, it’s no fun. If you hold onto your anger, someone cutting you off in traffic can ruin your entire day. So let it go.