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.
When angry count to ten before you speak. If very angry, count to one hundred.
Thomas Jefferson
But right now I like these MUCH better :):
When angry, count to four; when very angry, swear.
Mark Twain
Speak when you are angry and you will make the best speech you will ever regret.
Ambrose Bierce