Unlike most games this tournament, I got a promising position out of the opening. Then, when he threatened to create a dark squared blockade to shut down my initiative, I sacrificed a pawn. By move 21 all of my pieces were well placed and I had the option of regaining my pawn whenever I needed to. However, only a few moves later I started going a bit crazy. I felt that I had an advantage, but none of the variations I calculate led to anything better than some trades and maybe a slightly better endgame. Normally, this would be a great result against an opponent 150 points higher rated than me, but after having drawn the previous two games, I wanted a way to play for more. Instead of going into the endgame, I kept pieces on the board and played a complicated middle game, without ever taking the time to regain my pawn. As we fell into time pressure, my initiative slowly dwindled and my material disadvantage grew, until I found myself in a lost position. This endgame was worse than the games I had held in the previous two rounds, and despite attempts to complicate, I eventually took my first loss.
Summary: I over-pressed after a promising pawn sacrifice in the opening.
Lessons I should have learned: Don't attack just because you want to. Follow the needs of the position.