Handling unforgiveness is a daily battle if you don't want to be weighted down with other peoples issues. You have to make a conscious effort not to receive every little offense that is tossed your way. Think of it as a game of catch, if someone throws the ball to you, you have a matter of seconds to make a choice. You can hold out your hands and catch the ball or choose not to. If you don't participate, there is no exchange and therefore you've made the decision not to accept the ball.
Hebrews 12:14-15 (KJV) 14 Follow peace with all men, and holiness, without which no man shall see the Lord: 15 Looking diligently lest any man fail of the grace of God; lest any root of bitterness springing up trouble you, and thereby many be defiled;