Matthew 5:21 -- 26
You have heard that it was said to our ancestors, "You shall not kill," that whoever kills is liable to judgement. But I say to you, that everyone angry with his brother shall be liable to judgement; whoever insults his brother shall be liable to the council; and whoever says, "You fool!" shall be liable to a fiery Hell. So if you are offering your gift at the altar, and there remember that your brother has something against you -- Leave your gift at the altar. Go! -- First be reconciled to your brother; and then come and offer your gift.
Make friends quickly with your accuser, while you are going with him to court, lest your accuser hand you over to the judge, and the judge to the guard; and you be put in prison. Truly, I say to you, you will never get out until you have paid the last penny.
Anger is hell. Acting on it makes things worse; and the suffering becomes entrenched when one can't stop defending his anger.
Feelings of anger are no doubt unavoidable; but as one student of the subject concluded -- Anger is more than merely the emotion we recognize as 'being angry': "It's an emotion plus a judgement."
If you didn't feel that someone had harmed you, if you didn't feel he was at fault in the matter; you'd have no reason to be angry at him. Only God could do you serious harm; yet you become angry at this human being who, regardless of his intentions or his carelessness, has merely delivered your karma. There is no one worth fearing -- or being angry at -- except God.
If it's really God you should blame, what are the chances that you're missing something about what really happened and why it was necessary?
Clearly that's a figurative 'prison' in the last paragraph; and the debt is not a literal one. Still, if something inside is accusing you of being in the wrong, that's part of you. You don't have to agree with it; you do need to face what it's talking about and consider whether or not that's something you'd better recognize. If so, it's done you a valuable service. [But do keep in mind something that Jesus says elsewhere: "The Devil always was a liar."]
If you want to live in a world where the Spirit rules, and prayers have power to influence what happens -- then you need to clean up your act. God won't do evil; but wishing He would could only weaken your faith.