In my experience, couples I know who have divorced experienced one of two scenarios:
a) The man was not willing to keep to his marriage vows and engaged in adulterous behavior
or
b) The woman bought into a bunch of Oprah-esque pop psych philosophies that she had a “right” to be absolutely happy. Something that is utterly unattainable on this Earth, and which no man is able to provide.
Re point b) — I was reading an article on CNN the other day (clearly targeted at women), and one quote that struck me was, “no matter what your feelings are, they are completely valid.”