I agree it's frustrating, but I usually find that after I've played it through a couple of times, it comes back to me. The other day I dug out a piece that I hadn't played in literally 50 years, and I was surprised by how much I remembered.
About three months without playing something at least once I have found to be my limit in this regard. After that I need a few minutes fiddling to make sure of things again before being able to play it right through. I have no idea if this is better or worse than average.
No, that's completely OK. Nobody said you should be able to play it as well as the last time you did it. But don't you find you can get back there fairly quickly? At least within one practice session?
Does anyone else get really frustrated when you try to play a piece for fun that you've completed after working on it for months, let's say, a couple weeks after the big performance only to realize that you have memory lapses and it's sloppy? I know it's really trivial, but I just get this feeling like all the hard work has gone to waste. Has anyone felt this way before? Sorry, I feel I needed to vent a little...
In my own experience, I find the pieces that mean the most to me are the ones that are hardest to forget. I discovered that if I didn't like what I was playing, then I'd forget to the point, where I'd be surprised how I learned it the 1st place.When I lose memory of a piece, it's one of the following- I don't like it- People say I play it badly- It's low standard- I'm not worthy of having the piece in my repertoire- I make a mistakes despite playing that same piece for years- I have trouble playing in strict time Those self-sabotaging beliefs are ultimately what cause pianists to forget what they learned.