In your dojo. You know the one. Might be one of your instructors, might be all of them. Might be a guy who started with you, might be a guy who started just a few months ago, might be a guy who's been there for years, might be a guy you just stay away from. That's the guy you should spar, that's the guy you should hook up with to train with. That's the guy you should shadow, and bang with until he kills you....or not.