For the past month, I've been doing "The Swan" and tonight we finished with it, moving on to a Mozart minuet. I'm getting disturbed at how I perform on these pieces. Generally my very first attempts, when I first play the piece and the first lesson afterwards, are the best ones. Then it starts to get fuzzy; I fixate on the passages I find most difficult and get sloppy with the rest, mistakes made while practicing on my own get burned into memory, and the piece stops improving and begins degrading. I have no idea how to fix this.
Also finished the lengthy etude that I've been practicing concurrently with "The Swan" and moved on.