tournaments! how do I stay consistent?

I have the same problem.  What helps me is to play against a wide variety of styles and skill levels in practice games.  It is easy to look good and get confidence counterlooping back and forth against a high level attacker, but it is much harder to get in a confident groove against a junk player or someone who just pushes and pushes or gives you balls with little spin or pace.  When you play these people, maintain your confidence and aggression.  This will help you blow these players off the table in tournaments rather than shrink under the pressure.