Certainly these are the expressions we're looking to generate, but life often doesn't work that way.
Even great players manifest bad body language.
I'm guessing Blake Griffin questioned an official's decision.
The "shirt in mouth" doesn't exude confidence.
Even blind athletes assume the "victory" or "Pride" position.
Some coaches work to limit expression. Danny Ainge said of Brad Stevens, “Sometimes people can misinterpret competitiveness by facial expressions and demonstrative and yelling and screaming and throwing coats. He has a great control of his emotions, a great temperament, and is not nearly as demonstrative. But he is extremely competitive.”
Amy Cuddy reports (along with neurochemical changes in testosterone and cortisol) that body language shapes who we are. Better body language correlates with stronger performance and better results in job interviews. We can consciously control and improve our body language.
Notre Dame coach Mike Brey discusses body language in this brief video.
The Genard Group has a body language 'cheat sheet'.
As coaches, we should avoid conveying dismissive or negative body language to our players (closed positions, back turning to players, excessive finger pointing, unintended tone of voice, etc.). That doesn't mean ignoring play or behavior deserving correction. But we should make an effort to maintain control to get the desired results (better decision-making or behavior).
As players, increase your awareness of how your negative behaviors may adversely impact teammates, coaches, and officials.