This is a research-backed process for letting go of a grudge. Yes, there are 9 steps. Here are the first two.

1. Know exactly how you feel about what happened and be able to articulate what about the situation is not OK. Then tell a few trusted people about your experience.

2. Make a commitment to yourself to feel better. Forgiveness is for you and no one else.
Nine Steps to Forgiveness — from Greater Good