When you separate after a very long-term relationship, like 20 or so years, there’s a big partner-shaped hole in your life. For better or worse, someone has been by your side for all that time and you don’t quite know how to go about it (it = anything) alone. You feel disoriented and lonely and cold in the big world without an automatic, unquestioned ally.
So you might feel quite anxious to fill that gaping hole because its presence is so uncomfortable. It’s easy enough to do—you just take up with someone else.
That initial sense of relief quickly becomes a sense of confusion, because all of the expectations you have of that person are all about your experience with marriage and/or your experience with dating before marriage. They have nothing to do with that person to whom you’ve assigned the partner role.
So it all falls apart in short order and then you’ve completed your required Disastrous Rebound Relationship.
Luckily for all of you, I did that last year and will spare you any account of it. Further discussions of midlife dating will be forthcoming.