Getting even means indulging in negative fantasy.
One of the enemy's easiest attacks is getting Christians to go for a false balance.
Only the Lord knows what needs to happen. Only the Lord sees it all. Only the Lord knows the heart. And, He has commanded that you do not return evil for evil. He has also said vengeance is His.
It doesn't feel like evil for evil, does it? It just feels so strongly that something has to be done. The offense just can't be ignored. And, how will it look to others if you do nothing?
The only way to deal with the root of the matter is to go before the One who says you must forgive.
What is the beginning of forgiveness? The letting go of the flesh's insistent scream to say or do something. To somehow even the score. To teach the person he is wrong.
Much of the false balance is created in talking to others about the situation. In matters concerning believers, spreading negative information (whether true or not) gives the enemy access and energy.
Soldier of The Cross, come before the One who is All Power and leave it with Him. Is He able to deal with it? Does He know more about the situation than you?
Stop talking about it to everyone else and take it up with Him. The Holy Spirit will calm you and He will assure you.
Do it aloud.