Hey Smiles
I also train in BJJ and Thai kickboxing. From my experience MOST of the really good BJJ'ers are the nicest guys I know. You'd never know from just looking/talking to them that they's be able to take care of most people in a fight. Having said that, like someone said, as long as you don't act like a jerk I think your personality will be more of a factor.
When I do need some confidence it comes after a good day of training whether it's during lifting and seeing the gains, or when I'm doing kickboxing and my cardio is better than my training partner; or when you're kneeing from a clinch and your partner tells you how brutal they are. Just use things like that.
BTW who do you take BJJ under?