Confidence. That's huge as an actor. Confidence can get you a long way. Maybe it's a cultural thing, being Korean, but my first reflex has always been to exude humility - but it doesn't help you in acting. For acting, humility isn't the best thing. It'll weaken your work. So it's a head game for me. "Can I really be confident in knowing my skill set is down? Can I perform like I own this role?"
