Just wanted to share this article with you all. Although it cites swimming and running, it's probably very applicable to paddling as well.
From New York Times
HEALTH / FITNESS & NUTRITION | October 2, 2008
Personal Best: Before Hustling to Finish, Relaxed Is a Good Way to Start
By GINA KOLATA
Trainers and coaches say relaxation is crucial to a strong performance, and tension only serves to diminish an athlete's performance.