May the LORD judge between us. Perhaps the LORD will punish you for what you are trying to do to me, but I will never harm you. (1 Samuel 24:12 NLT)
David was being hunted like a wild animal by King Saul all because of his insane jealousy of him. When David had the opportunity to avenge himself on the king he refused and left any punishment of him to the justice of God. It's so easy to let self-imposed vengeance spin out of control! But, the right thing to do toward those that have wronged you is to give them over to God. Only He can deal with them justly, do it at the appropriate time, and utilize the proper means.