Holding anger is a poison. It eats you from inside. We think that hating is a weapon that attacks the person who harmed us. But hatred is a curved blade.

Holding on to anger is like grasping a hot coal with the intent of throwing it at someone else; you are the one who gets burned.
Buddha.
Anybody can become angry - that is easy, but to be angry with the right person and to the right degree and at the right time and for the right purpose, and in the right way - that is not within everybody's power and is not easy.
Aristotle.
Anger dwells only in the bosom of fools.
Albert Einstein
He who angers you conquers you.
Elizabeth Kenny.
Whatever is begun in anger ends in shame.
Benjamin Franklin
When you are offended at any man's fault, turn to yourself and study your own failings. Then you will forget your anger.
Epictetus