You know how you feel when you've been drinking the night away and you wake up? And you are lying next to this cute guy and it all starts coming back to you bit by little bit? And you lie there smiling, wondering what he would remember? And how he would feel about it in the morning? And then (if you're me, at least) the bathroom beckons, so by the time he's up you're in the kitchen making coffee, so he's completely knocked offsides and really doesn't know what to say to you.
And then you realise that guys get more embarassed by one-nighters than girls do. (That is, say, if the girl we're talking about happens to be anything like me.)