What kind of body language do you display when you are playing your sport? Do you wear your emotions on your sleeves, or are you stoic and hard to read?
Most athletes get excited during positive or negative plays during a game. The key is to make those emotions short-lived and being able to move on to the next play.
Positive body language tends to inspire a team and the coaching staff. Negative body language does just the opposite. Set the right example for yourself and your teammates. Even if things aren't going your way, don't let the opponent know!