I've been playing WTC Book 1 Prelude no. 17 for quite some time now. I got it up to near perfection from a technical standpoint a while ago, but then I stopped playing it for a month or two and now I'm coming back to it. I find I'm having a lot of difficulty though. I've been working on it for two weeks and I just keep getting frustrated. The first week went quite well, but now, I've been quite inconsistent. Some days, I'll play through the entire thing and not miss a note, hands perfectly together, and it'll sound great. The next day, I'll try playing it and my hands turn to mush. When my hands turn to mush, I'll slow it down to 60 or 80 bpm and play through it. As if the inconsistency there isn't frustrating enough, this morning, before going to work, I tried playing it at a quite slow tempo and I just...I don't even know what happened. My fingers couldn't play evenly. The 16th passages sounded like a drunk person trying to walk, or as if I were trying to add a slight swing to the notes. It's just so damn frustrating and I don't know what the problem is. One day, it'll be fine, another, terrible, and I just make it worse because when I get frustrated, instead of taking a break, I just have to keep playing. Last night, I was honestly so upset when I went to bed that I just wanted to quit piano altogether (though I know I'll never go through with it!). I feel inadequate.
Can someone please help me?