This is one of the few areas where I kind of disagree with Mari. I only listed reasons when I was confronted by someone who was tenacious & didn't take no for an answer... otherwise, I didn't explain anything other than that the relationship was not right for me at the moment (and if there was another man on the scene, that this was the reason).
I came to this decision after reading a number of explanations of how lots of people think women prefer bad boys... because whenever we break up with ANY boy, we start out with some version of, "you're a really nice guy, but..." suggesting that we don't want to DATE the NICE guys, just the bad ones. It's not true. the truth is usually that the guy we're talking to is not as nice as we want for ourselves, but we're all full of trying to spare their feelings and boost their ego and make ourselves feel better for being so nice about the breakup & not "hurting" them.
A breakup is a breakup & no number of "you're a nice guy, but..."s will change that.
Though Mari's open position on explaining her expectations in bed is admirable (and probably quite effective).