The piece that was kicking my butt last night was Wassolonka. My energy was so low I just couldn't focus at all and was messing up even the pieces that I did fine with last week. Then, we learned a new part that is actually three elements strung together. None of them, on their own, is that difficult, but for some reason I was just completely unable to put it together.
Today, I sat down with the recording and worked my way through it. The key, for me, is practice. I have to get to a point where I don't have to think about it anymore. It has to stop being cerebral and work it's way into my muscles, my heart, my body. Then I can play a piece without errors.
I still have a long way to go with Wassolonka.