What makes a man behave aggressive durin sex? it boeders with sadism actually..?

[mayavalerya]

My bf really enjoys rough and aggressive sex. It surprised the hell out of me when I started enjoying it too.. He loves to see me in pain and I'm really ok with that because I like it and he's really caring and gentle otherwise. I just want to understand what brings this urge to hurt me during sex? Why does he enjoy seeing me suffer? I'm guessing the next logical question would be why I enjoy it too! P.S. He's in the army

 

[Stargazer]

there was song about this I heard years ago "It's a fine line between pleasure and pain"
http://www.youtube.com/watch?v=_aYzQb6cc5E

You probably just like the feeling of someone who is in control. If you are both fit individuals it sounds like it is also a work out too, so it's a similar thing I guess, release of endorphins etc.