I used to be the same way as you. In fact I was probably even worse. Same day matches weren't as bad for me as matches down the road like at the league or regional tourneys. If I had lost to a guy back in November I would carry that with me through the rest of the season or even into the next.
Well I lost to this guy last year so I'll probably lose again. It wasn't until I got older that I realized how negative an impact that sort of thinking has on your success. I regret holding onto that thought process for so long, I wonder what if I had gone into each and every match with a new outlook or desire?
And in fact, that is the great thing about wrestling or bjj. So what if you lost a 6-8 minute match? You are more than likely going to get another chance so make the most of it. Learn from your mistakes and capitalize on theirs. Show them and everyone watching that that wasn't the "real" you before, this is.
Don't think about what they did last time or what they may do this time. Think about what YOU are going to do and that's it. See yourself doing these things and not reacting to things he might do. You can only control your own thoughts and reactions right?
For comparison purposes (all were on varsity) - 9th grade, 101 lbs, 5-12; 10th, 101 lbs, 11-9; 11th, 122 lbs, 14-8; 12th, 135 lbs, 20-8. And 12th grade was the only year I ever placed at state.