I don't mean to get overly psychoanalytical here, but many, many of us are moderately dissatisfied with the general state of things in our lives. It may not be a full-blown misery, but more of a background unease. That's why many of us seek novelty - new surrounding, new sexual partner, new activities. Oftentimes it's all in the name of "creative challenge," but it's undeniable to we do things to mask the overhanging unease of our lives. How is this relevant?
I think that, whenever there's a change in social dynamics, whether due to physical separation, conflict, etc., we tend to see in it an opening, a pad for launching a new life, a new beginning, although in a small way. As cruel as it may sound, getting rid of a person who's made up a significant part of one's life can be a great excuse for seeking new social circles, trying new things, etc.
Or it may just be the old adage "Out of sight, out of mind," proving to be true. I personally find it very much to be true.