When we are at odds with someone, our natural response is to get even. They treated us badly, so we respond in kind. But while that is our natural reaction, is it the proper response? According to the Bible, no, it is not.
Proverbs 24:29 says, Say not, I will do so to him as he hath done to me: I will render to the man according to his work.
The desire to get even is called malice, and the Bible has much to say about it.
Let all bitterness, and wrath, and anger, and clamour, and evil speaking, be put away from you, with all malice: - Ephesians 4:31
But now ye also put off all these; anger, wrath, malice, blasphemy, filthy communication out of your mouth. - Colossians 3:8
Wherefore laying aside all malice, and all guile, and hypocrisies, and envies, and all evil speakings, - I Peter 2:1
Lay it aside. Put it off. Get rid of it! Malice is a vengeful and spiteful attitude that can harm friendships and testimonies. It is the desire to seek restitution for the wrong that has been done to us, and it can be overwhelming. Malice often exposes itself in phrases like, "Serves you right!" or "That's what you get!" It revels and rejoices in the misfortune of another because, in some warped form of justice, we feel they deserve it. And while the person who wronged us may indeed deserve consequences for their actions, it is not our place to dole out punishment. That job belongs to God.
Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, saith the Lord. - Romans 12:19
So, dear ones, I urge you to lay aside all malice. Give the issue and the offending person over to God, and allow Him to resolve the problem. He will ensure that the punishment fits the crime. And as for you, you will rest easier and find more peace with a heart that is not cluttered with malice and bitterness. Give it all to God. He'll take care of it!