My thoughts based on my experiences.
Usually when a couple gets to this point it's more often than not due to a whole lot of built up resentments, underlying problems and issues that have never been rectified. Many times the true issues that are the root of the problems have never been addressed effectively much less rectified. Underlying problems/issues and resentments in a relationship fester and slowly poison the entire relationship not just the area in which the problems/issues/resentments started. Fighting about everything, bickering over little things, back biting, baiting one another, playing tit for tat and so on are usually just systems of bigger issues that need to be taken care of. Most people just react in those ways because they do not know how to honestly, openly and safely communicate with one another about the real deep issues that are the true problems.
at 3:03 PM on Jul. 10, 2011