boys.

though i haven't experience one.

sometimes, they'll date other girls just to forget the other one. easy eh?

or sometimes, they'll drink a lot of alcohol and the next day, poof! they've forgotten the girl, and, they actually moved on.

for girls well. girls are emotional. if they want the boy, they'll do everything of course. their earth/world is one, and it's [i]him[/i] and, if they.. you know, breaks?. they'll cry every evening and regret why they let them loose the guy.
oh well. that's life, better accept it ^^