People say ”forgive and forget” because they twisted up a passage with origins in the Bible where God says of those of us who are grafted in has His children that he will take our sins and dropped them into a bottomless ocean, so to speak, never again to remember them. By that, people believe we as people should have the same capacity when we can’t. in fact, you are not supposed to forget, because if you did, you could set the person up to repeat the injury they done to you. However, as others have said, you acknowledge they did that, but you don’t hold malice or thoughts of vengeance against them, especially if they apologize.