From Jack Zavada
http://christianity.about.com/od/singlesresources/a/avoidbitterness.htm
You take the first step by going to God and asking him to be in charge of your justice. You've been hurt and you want justice, but that's his job, not yours. He is the One who makes things right. When you return that responsibility to him, you'll feel a heavy load come off your back.
You take the second step by thanking God for all the good things you have. By concentrating on the positive instead of the negative, you'll gradually find joy returning to your life. When you understand that bitterness is a choice, you'll learn to reject it and choose peace and contentment instead.
You take the last step by enjoying and loving other people again. There's nothing more attractive than a joy-filled, loving person. When you make that the emphasis of your life, who knows what good things might happen?