Deep Practice and reps of one piece; not doing it all at once
My teacher told me to find the few bars that are causing the most trouble and practice them 8 times or so, and 20 times if it is just a few finger movements you can't seem to get. I do this a lot.
I've found this month when I do this, my hands hurt in the evening and on the next day. This is not good, says me. So what I do now is have seven reps of four bars, then I move onto the other difficult bars. However after my break, I don't return to this same piece. I do something else on my agenda, which for me is the next item on my todo list for today.
This has caused the pain to go away. By the way, I practice with a timer, and I set it for 27 minutes at the start of my practice, and after several breaks, it goes down to 15 or so minutes. This is a way to give my body more rest when it's been hammering at the keys for awhile. I take a 2 minute break between these 20-ish minute sessions, which is also sort of timed, and I don't make tea or anything while I'm practising; that's for when I take my main breaks after around two hours (basically when my pot of tea runs out, for me).
I've learned not to practice over 20-ish minutes. It really causes fatigue. When I was first playing this amount was 15 minutes MAX. Now I can do 32 minutes at the beginning of practice, most of the time, if I feel so inclined.
I tried to practice my reps with a metronome, but mostly this has caused me to spend hours on reps that I now think are wasted. When I don't use a metronome (on the reps), I can take the needed time to see the next note, and ensure my fingers are ready and then play correctly. When I was using a metronome, I would try to fit all the notes onto the beat, and therefore had to rush my fingerings, and there were two outcomes. One was to repeat the same mistake, trying to catch up to the metronome. The other was to restart the section again and again until I got it right, and on time with the metronome. The latter took up very much time, and so now when I get reps that I can't seem to play with a metronome yet, I dispense with it.
Dust on my keyboard is one thing, but a hair? It just has to go before I can play, otherwise I think I'll fixate on it, lol.