Breathe

Relax and breathe.  This is a simple concept but one that is easily missed when trying to get in the best workout.  Your body works best when muscles are relaxed and muscles won't be relaxed unless you remember to breathe.  When you sprint most people know that it is important to breathe and to not tense up your muscles.  This works for training as well.  so, next time you work out remember to breathe.