I think that breaking up can be a metaphor for "getting clear". The babyboomers, long years ago (as my 4 year old granddaughter puts it), felt the inclination to "find ourselves". For women, it's an evolutionary step for human-kind. And it correlates with menopause, the age Buddhists believe to be "adult", finally. When we lose our eggs, our priorities change. We can find out who we are without the overriding need to create other-life. In deed, it's time for our own.
Every time I break up, I "find myself"-- on a deeper level. And it gets harder to recognize who I used to be and what I was willing to accomodate.
As we age, our relationships need to be refined or even redefined because we have become every experience we've had. None of us get out of here without history. Who would want to?