Dr. Hates
Jerk.
Despite what people have said about modulating your expectations (and it's good advice, really), from the moment you sit down to play until the moment the final round is over and somebody moves on, expect to win. Don't get nervous. Don't doubt. Hell, don't even respect your opponent. Make them earn every bit of that. The worst thing you can do is psych yourself out and make losing a self-fulfilling prophecy.