Please bear in mind the phrase "the blind leading the blind" when reading my reply and hopefully somebody much more experienced will have better advice to offer!
QUOTE(Mini_mo @ Sep 20 2009, 09:09 AM)

Even though I know my notes in both clef pretty well, my old ailling brain cannot read them fast enough to track a piece I have learnt.
So to begin with when I am reading the notes and playing the piece, it may not be totally fluent and up to speed. Then once it is all up to speed and fluent, my finger memory takes over and I seem to no longer be able to track the music on the page.
When you say "reading the notes", can I check that you're reading the chord or the pattern rather than the actual notes? I think it's impossible to read all the notes - I think the idea is that you recognise a pattern (a scale, an arpeggio, an inverted chord....) and your eyes skip along from one pattern to the next. So rather than reading 30 notes or whatever, you only read 5 patterns, say. I'm sure you are doing this but I thought I'd better check.
QUOTE(Mini_mo @ Sep 20 2009, 09:09 AM)

Learn piece by reading music.
Piece is fluent with a couple of wrong notes.
No longer bother reading music as I realise I am not really looking at it anyway.
Then continue to play to keep up piece to same level.
Then it starts going downhill, all different mistakes all over the place.
Get the music out again and go over in fine detail parts that I make mistakes.
Other mistakes then occur and the process is never ending!
I've posted something similar in the past, and apparently this is just muscle memory which is unreliable. If you haven't already done so, I would suggest that you study the music and work out the structure. I take a photocopy of my music and use a highlighter pen to mark repeat sections, for instance. I've also recently started studying the structure of individual chords... so in a sequence of chords, the top note may remain the same and only the bottom two notes change. Seeing this pattern has really helped with some of the pieces I'm working on.
Try and force yourself to keep looking at the music, even if you're just skimming it, so that at least you absorb/retain familiarity with it. To really get to know a piece well, you need to start at different points in the music. This is quite time-consuming, and it may depend on how well you need to know the piece and the reason you're learning it. If you're learning it for a concert or an exam, I would think you need to do it, but if you're just learning the piece as a means to learning a new technique, rhythm etc, then I personally wouldn't spend time learning the piece to that standard.
QUOTE(Mini_mo @ Sep 20 2009, 09:09 AM)

Actually I would just like to add that one thing I really struggle with is playing through my mistakes. When I do make a mistake it really throws me and I cannot continue. If I could I guess it wouldnt be so bad.
I think this is just practice. I'm getting slightly better at it, I think, but I agree it's not easy. I think it's easier if you've studied the music and started at different points, ie as mentioned in my other paragraphs above.
I've posted on something similar to this in the past and I tried to find it earlier but couldn't. What I did end up reading though was a couple of threads that I started when I'd only been learning the piano a few weeks. It was really funny to see that I was agonising over a piece which I can play really easily now

So don't despair Mini_mo... it's just one of the many hurdles that you'll reach - and cross - over your playing lifetime. It just takes time, and practice, and hopefully some better advice than I've given here!