How to let go of anger/hatred for someone?

Its natural to feel anger against someone who wronged us. We were created with a sense of justice and so we feel that to remedy to situation we should HATE them as if that some how hurts them and 'serves them right'. In reality though, all it does is harm you. It harms your mental health AND physical health and scientists are just NOW discovering. No, its not easy to let it go. But, I try to remember that: A: it harms my health, B: it is really NOT doing anything to the other person, and C: its always best to forgive and forget if at all possible.