If it’s still upsetting you when you think about the pain they caused, then realize that the upset has nothing to do with them. It’s coming from you.
Revenge and anger will do nothing to relieve you, only forgiveness can. If you’re still upset, then you haven’t fully forgiven them or yourself. You have to forgive yourself for whatever you think you did to bring that hurt into your life to begin with. Forgive, so you can move on.
I believe that what Jesus meant in his teaching to “turn the other cheek,“ was to turn away from whatever transgression has hurt you, and turn towards the peace and happiness that you want.
What we focus on expands, so stop looking at what hurt you. Turn your focus instead onto what you do want, which is peace, happiness, and joy.
Forgive and move on, it’s the only way to stop letting the past hurt and upset you.