Consider Proverbs 17:9, which reads in the ESV, "[w]hoever covers an offense seeks love, but he who repeats a matter separates close friends."
There are basically two responses to the wrongdoing of your friend. You can, as they say in Brooklyn, "forget about it" or you can act in the same way one's credit report does—that is, holding every delinquent payment against them. Friendships are meant to last but cannot if they are a score-keeping struggle. There will always be disparities, but the goal is not to get even. The goal is to give your best. If you are worried that the other person isn't putting in the same amount of effort as you, sure, you could bring it up, but it is not necessarily what's best for your relationship. So, what is?
Paul explains in his first letter to the Christians in Corinth that true love doesn't keep a record of wrongs (1 Corinthians 13:5). For the Christian, it cannot be that we hold the mistakes of our brothers and sisters over their heads. Does this mean that we shouldn't hold people accountable for their actions? Certainly not. This verse speaks to a healthy Christian relationship. In a healthy relationship, the two parties will not be engaged in constant offenses against one another. When this happens, the relationship cannot be defined as healthy and will not likely be a relationship for much longer if the problems are not acknowledged and addressed. To keep a healthy relationship healthy, each person must make a habit of not bringing up the mistakes the other has made.
If someone is constantly causing offense against you, perhaps the best thing to do is withdraw. Especially in cases where there is violence (physical or verbal), the victim should not pretend like nothing wrong is happening. I pray you never find yourself in a violent relationship. This advice is not for such cases. When the other person is causing you great fear, seek help.
If you find yourself continually bringing up a friend's (or, spouse's) wrongdoing, ask yourself why you keep doing it. Do you think that relationships are supposed to be (or, that it’s even possible for them to be) even, 50/50? Are your own insecurities leading you to point out flaws in others to make you feel better about yourself? Could you be worried that the hurt from your past will repeat itself in the future? Whatever may be the reason you keep bringing up your friend's past mistakes, it cannot continue if you want the relationship to. There may be some difficult conversations that need to take place, but a little difficulty now is worth the chance of saving a relationship, making it stronger, or even changing the type of relationship it is (if it’s for the best). Relationships cannot flourish if one or both parties are holding on to the hurts of the past. Forgiveness is essential for relationships with others. When we bring up hurt, we are showing that we're still holding on to offense and maybe haven't forgiven the other person.
If you are the one in the relationship whose action keeps getting brought up - be sure that those actions that are mentioned aren't something you keep doing. If you keep doing something harmful maybe you shouldn't be surprised if a human being with feelings keeps bringing it up. If it is something for which the other person has supposedly forgiven you, but they won’t let you forget it, let them know that their continuing to mention it is hurting you and making you feel like they haven’t really forgiven you. This may be a tough conversation. Perhaps the other person doesn't realize that it hurts you (hopefully, they don't realize it). But make sure it doesn't become a score-keeping battle. It is entirely possible that you don't realize you're doing the same thing to them. Make sure you are aware of how you are speaking to them and how it is affecting them. And always remember that love covers a multitude of sin (1 Peter 4:8).
-Joel Fletcher