I struggle with that too. Maybe we don’t need to forget. But when I don’t want it clouding my thoughts anymore, I try to think of a reason with myself in their shoes what could have caused their words or actions. I can usually come to a conclusion that helps me understand them better, then with that perspective it helps me drop the situation from recycling through my mind. Also when the thought pops back up, I try to replace it with something happy & exciting in my own life. That helps too, but can take a lot of times to stick.