I know it, and not even in marriage, but in every partnership. And it’s a constant. Even though you may have promised, the emotions and true feelings can change and frankly not necessarily for noble reasons. The best way to understand this dichotomy is to look at and consider Maslow’s Hierarchy of Needs, which imply that needs have to be met or else they linger and disrupt the whole being. I wasn’t satisfied sexually in a relationship and along came someone, who satisfied that need, while all the others were unmet. The fact that the former person satisfied those needs, it took time to realize the mistake. No one is perfect, but needs direct our behavior. Two people need to align in terms of their needs, then they might make it.