Old fights get worse every time you retell them. Try telling it once the way the other person would.

Each retelling adds a little: a worse motive, a sharper line, a detail that fits the version you prefer. The story hardens while the event recedes, and after a few years you are angry at a construction rather than a memory. Telling it as the other person would is a way of loosening it, not of excusing anybody. You can do that and still think you were wronged.

Take the fight you have told most often and tell it once from their side, with their reasons included. Notice what you leave out to keep your version intact. If it is genuinely old, you are allowed to stop telling it.