lol..good question..i don't know if it's the mixed emotions involved that make it so AMAZING or not. I would guess that the fact that u still may be mad (possibly makes u more aggressive), horny, and excited all at the same time releases that many more "endorphines". i'm no doctor, but it's a guess..maybe that's y some people tend to argue more than others...just to set up the whole "make-up-sex thing" afterward..lol