Exhale

By Meachrm @BaseballBTYard
Here is a quick tip for any player who recognizes that their nerves are getting the better of them in pressure situations.  Correctly time your exhale.  The human body reacts differently when we inhale versus when we exhale.  When someone is startled or frightened they usually gasp which means they inhale quickly and tense up.  When the moment passes and they realize they are no longer in danger they relax with a big exhale … “Phew (exhale), that was a close one!”  Knowing this, players can use the power of an exhale to their advantage.

To help relieve tension, a hitter can be slowly
exhaling at this point in the delivery.

In order for pitchers, hitters, base runners, and fielders to get the most out of their bodies in terms of quickness and power, they need to be fairly relaxed to allow their muscles to be free of tension.  Squeezing the bat too tight slows bat speed.  Squeezing the ball too tight slows throwing velocity.  Tensing up right before you need a great jump to steal a base slows your first steps.
Try this.  Right before you need to perform, start your exhale. 
A pitcher can exhale slowly as he starts his delivery.  A hitter can begin exhaling just before the pitcher releases the ball.  A fielder can do it as the ball is released by the pitcher.  This is done to help relax the body so that it can function quickly and powerfully.  As stated earlier, inhaling tends to tense up the body, exhaling relaxes it.It takes some practice to get the timing down but you may find that something as little as this can have a positive impact on your ability to calm the nerves and perform.