When you hold a grudge, the truth is, the grudge is holding you. The other person, the one you are angry with, doesn't carry that negative feeling with him, only you do. Forgive him and your grudge will fall away.
Anger is a called a form of idolatry because when you are angry with someone you think the person who angered you did that bad thing to you, when in truth Hashem had him do it. Don't give your enemies so much credit.
Hashem called out, "Anyone available to do this bad thing to so and so?" and your enemy volunteered. Yes, he did it, but Hashem recruited him.
Why did Hashem ask for someone to be bad to you? I don't know. What did you do to ask for it? When you point a finger at the other guy, remember that three of your fingers are pointing back at you.
The simple solution; think good, thank G-d, be kind, let go… all easy and pleasant things to do... and you will live a loving, blessed life… all day long.
Be well