When we hold anger and resentment in our hearts, we are carrying burdens and making life more difficult for ourselves. We are the ones imprisoned by our sour attitudes and we are the only ones who can set ourselves free. Not only is it emotionally constricting, cutting us off from more positive people and experiences but it is bad for our health. This is a documented fact.
What do you do to free yourself? Forgive everyone who has ever wronged you. Make a list of people you have been angry with. Then go through the list and in your mind (or out loud if you prefer) I forgive you. I release you. I wish you well. Send love to that person. It is an extremely freeing exercise.