You are focused and ready for a huge battle.
You surprisingly win the first game 11-0.
You start thinking about how amazing you are playing.
You start thinking about how easy it is.
You aren’t thinking about strategy.
Your opponent relaxes and changes strategy.
You start losing in the 2nd game.
You are shocked by the change of events.
You start to mentally freak out and your mind goes blank.
You lose the match 3 games to 1.
This is a very common occurrence in tournaments across the US.  Be aware of the fact that the first game does not reflect the outcome of the match.  If you win the first game easily, keep your focus and determination.  If you lose the first game easily, then change strategies and be fully determined that you can come back in game two and win the match.