It’s easy to want to do. If someone makes you mad, to calm yourself down from them taking advantage of you, you figure out a way to get even.
Everybody has a tendency to do it to one extent or another. Even family members do this with one another. One brother breaks another brother’s toy so the one with the broken toy gets even by destroying a favorite toy of the one who caused the offense.

Even when someone has spite towards another or holds a minor grudge against an offender, in a minor sense of the word the person harmed is still getting even.
In the eyes of God, revenge is wrong and Christians must make a conscience effort to fight against the angry thoughts and then the revengeful deeds. They must instantly, in most sincerety, quickly pray to God to help them to fight against the angry, bitter thoughts.
In adults, revenge gets worse. Older adults, mid-thirties and up, know well the practical application of psychology to relationships. A revengeful adult can use this against a person whom they are angered by the psychology of the specific situation. Most adults can quickly figure out the personality (strengths and weaknesses) of another. Then they can use their psychological weaknesses and get revenge through their weaknesses.
Personally, I consider the ability of quickly figuring out the personality of another a gift from God. It is a talent not to be abused. Many older woman use this God-given gift (It is even a stronger gift if the woman has had children.) against younger women who are still attractive to men. If God gives you a gift, be thankful for it and fear Him enough to not misuse it. He can remove talents from your life, especially if you are a Christian, if you are wrongfully using them.
In the Bible, it says, “Vengeance is mine thus saith the Lord.”
Not dealing with angry thoughts (just getting revenge instead) is harmful. Unresolved angry thoughts lead to bitterness which can lead to wrong outbursts of anger and depression. Depression leads to less happiness and less success in life because you spend your time in self-pity constantly telling yourself I don’t deserve what has been given me rather than having the adventurous attitude that life is full of struggles. When you overcome struggles you build confidence in yourself and you gain an accomplishment that years into the future you can look back and say, “I’m so glad I did that.”
Elizabeth Elliot talks of bitterness in her devotional Where There Is Injury which is found on today’s Back to the Bible website. I love the quote at the end by the famous Saint Francis of Assissi from so long ago:
Have you ever found the taste of revenge sweet? Does there lurk in your heart, as in mine at times, a desire for at least the milder forms of revenge if you have been hurt–a desire to see the person apologize, an urge to remind him that he was nasty to you, or even the temptation to pay him back somehow? It was not God’s plan that man should take revenge. That He has reserved for Himself, and when we seize that power we are taking a huge risk. It is, in another form, the risk Adam and Eve took when they ate the forbidden fruit–arrogating to themselves powers, lethal burdens, for which they were never designed.
What if God paid us for our sins? What if He were not Love? His mercy is everlasting and has brought us salvation and forgiveness. Remembering that, and how we ourselves have offended Him times without number, shall we dare to retaliate when someone sins against us? Think of the measure of forgiveness God has offered us. Think of the price. Think what the cross means. Then pray the prayer of St. Francis:
Lord, make me an instrument of Thy peace–
Where there is hatred,
let me sow love;
Where there is injury,
pardon….
For it is in forgiving that we are forgiven,
It is in dying that we are born again to eternal life.