Often we forget that there are others around us facing difficult times. We are not the only ones. Take time to think and feel for your fellow humans.
Its likely those that have harmed you rarely think of you. Do not give them the satisfaction of occupying your mental space. Try to stay away from poisonous thoughts. If you seek revenge, the outcome can and will harm you both.
For me it helps to meditate with my crystals and re-center myself before giving in to anger, or letting it fester.
I believe it was Ghandi who said "An eye for and eye makes the whole world blind." Good food for thought, especially now.