I know why people carry anger for a long time because I’ve done it myself. It doesn’t make us happy, but it does offer some powerful advantages: we have moral high ground and can “righteously” despise the one we think hurt us, and anger helps us justify ourselves and blame others. Letting go would just let the other person off the hook. And angrily bringing up old hurts is a weapon in our arsenal that we can bring out when it’s helpful to win an argument or fight.
But anger is toxic, poisoning the mind and belly. Anger is prison, and only we have the key, because it is a self-imposed imprisonment. You and I are not destined or forced to stay angry. It is a sick choice we make. The gospel of Christ calls us to a different way, a better way: “If it is possible, as far as it depends on you, live at peace with everyone. Do not take revenge, my dear friends, but leave room for God’s wrath, for it is written: ‘It is mine to avenge; I will repay,’ says the Lord” (Romans 12:18,19).
Those who have been forgiven much by the Savior can demonstrate that their gratitude is real by showing mercy to the other fools and sinners around them. Furthermore, you don’t have to fear that someone who has hurt you is going to get away with it. God saw everything and will take care of the punishing in his own way.
Give it all to him. Right now.