When I've finally come to the decision to end the relationship, I usually cut it completely clean. No friendship afterward. If I am the one making the decision, it has to be for an extremely serious reason. Usually, I stick around in a relationship long after I should have left. The wishful thinking comment is the best to describe it. I guess I always end up hoping for the best, or for a change, or for anything to sway me from making the decision to cut someone out of my life.
If I am broken up with, though....oh boy. Yikes. It's like, I'm scraping for some sort of reason! Usually, I have been lied to about the breakup. Just recently, I had someone leave me hanging... he won't return my messages or anything. Just dropped off the face of the planet. I continued to write him emails, even though it's probably better that we didn't end up together. Something about ending a relationship with anyone I've grown close to feels like getting kicked in the gut.