Sudden setbacks when learning a piece

[piulento]

Hi, just wanted to know if anybody else experiences this:
You start out with a certain piece. You play it for a couple of days, and everything goes wonderfully. After about a week you can play it by heart at a pretty good rhythm with very few mistakes. You're sure that by next week you'll be able sit back and enjoy the piece while you play it effortlessly.
And then one day, you sit down and practice, but something's just wrong. You can't play it anymore like you did. Yesterday you played it just fine, but today you somehow got back to day 1 of learning (or even worse) - you suddenly don't remember most parts, you can't play some of the sections at all, and the ones you can play sound like s**t. The piece also sounds strange and unrelatable to you. And it doesn't go away after some practice. You somehow just lost the piece over night.
One might think about this - "you're just listening more carefully and with higher standards than before, nobody can get that worse over night". But it happens. It happened to me more than once. It happened to me this week with 2 pieces at the same time.
Does this happen to anybody else? Why does it happen? What can you do about it? I really don't want to switch pieces every time this happens.
Thanks in advance!

[danielo]

I think you have to keep a level head.....sometimes when I sit down to play, nothing comes out right, I feel frustrated, get annoyed, things go from bad to worse. This usually happens either when I'm tired, or when I'm just not really in the mood to play that particular piece.
Sometimes the best thing to do is just to leave it for a while. Play through it at walking speed, just very very slow, just get your fingers memorising the right patterns at a very slow speed.
I had to play a Rach piece in a recital, towards the play date, I was getting more and more frustrated, making mistakes in places I just didn't usually make mistakes in. The morning I was due to play, I just played it through at walking pace a few times, being sure to be very accurate with each note.
The recital went better than I could have hoped!