If you want to win you have to believe you are the best. You cannot accept failure. You cannot accept defeat. You are capable of beating anyone, even your instructor, and you must roll in this mindset. Whoever your opponent is, they are just another person.
In the words of my instructor, Dave Trader, "You have to take it personally and refuse to accept [defeat]. If someone beats you today you make it your mission to beat them tomorrow. You roll it back in your mind again and again and search for the error you made so you can correct it. That is what it takes to be a national or world champion at the highest level."
Defeat is not just losing a match, it is getting taken down, having your guard passed, getting mounted, etc. You can never accept this. You must give as much effort in class as you would in competition. You will compete the way you train. If you accept defeat during class, you will accept defeat in the tournament.
Believe you can beat anyone, and train this way.
Listen to the interview with Kyle Dake's teammate around the 4:00 mark.