Trying to forget a relationship means losing the entire experience and its lessons

Most of a relationship is likely positive. If it was not, you should have ended it sooner. So why would you want to erase all of that just because it ended badly? Forgetting is always the worst option because your goal in life should be to accumulate experience. It does not matter if you were unfaithful, if she was, or if there were fights. There were good things too, and erasing everything means you also erase the lessons. You stop being able to reflect on what you could have handled better, whether that was a specific argument, the breakup itself, or how you read the warning signs. That is when time in a relationship is truly wasted. Even a five or six year relationship is not wasted time if you genuinely reflect on what happened and use it to do better next time.