You want to do what the coaches tell you to do. You want to be aggressive. You want to be a valuable part of the team, to support the guys. You want to earn more playing time, more notice. You want to be a star and go on to play pro ball, command lucrative contracts, own cool things, be adored by a hot lover and a million followers on social media.
To boil it down farther, on defense you want to remember to move your feet, avoid collisions, quit being faked off our feet to block shots, and stop reaching for the ball when an opponent has it.