Why do you think they like to cling to the past? In relationships is considerably more common lead to the failures of the past, indiscretions, disagreements, feelings, problems, whatever. The problem is is that healthy? I would say that probably do not. Is it ideal? Definitely not, but unfortunately, we all human. If relations were always perfect day after day, then it would be a little boring. But the question is like forgetting the past in a relationship however, the fight continues over the past means that, or well, the two, it seems that they can not move forward.
That might be because it perceived that the feelings were not heard before, or because the problem still exists, but definitely is not doing well to any of you that comes every time. So, how to go ahead? Well, that has as much of yourself as an adult and to agree to let it into oblivion. If you or your partner are not willing to do that or are not prepared to continue, be honest and tell the other person what is happening with you, no matter how painful that is. Otherwise, they persist and persist and your relationship will break. If both are agree to move forward, with sincerity, then you need forget and move forward, really. The question that must be asked why not forget and forgive? Leave the past is not easy but it is vital these discussions can occur multiple times, but must be addressed otherwise never be will and my bet is that it will happen quite frequently if allowed that to happen. Keep in mind that sometimes things are going to happen for any reason, a fight or disagreement, or that the person feels upset by something that has nothing to do with you and is a way of expressing his anger. Many times we are the most critical judges of ourselves and often submit to the people closest to us by our frustration.