The subconscious mind is the seat of memory, and it will function automatically for us in a performance situation if fear is taken out of the way.
It's important therefore to focus down on what's happening in the current measure of music as we play, concentrate, and NOT let things distract us -- like a sudden unexpected burst of applause -- like someone asking us questions -- like someone wanting to shake hands (yes, they do this to us even when we're trying to sight read!) -- like mistakes -- or maybe some tricky place up ahead.
All of these things can trip us up by hijacking our eyes, ears, hands, mind, and attention.
From a purely mechanical standpoint there are no issues (save for physical limitations) which practice and having the right tools cannot solve.
When we play, if we make a little mistake, we don't dwell upon it -- we just leave it behind and keep moving forward ... it's in the past.
If we begin to start thinking about why we just made the mistake then pretty soon we're making a few more because we're getting distracted and not staying with the moment.
It can be aggravating when we know we can play it better and have done so countless times -- interference can enter the mind from any direction -- but we just need to chalk it up, forget about it, and keep moving, just like we would when we're sight reading.
The more we can cultivate the habit of NOT getting provoked with ourselves if a little blemish happens in our playing, the better our memory will function through the remainder of the music.
Some of the best advice we can receive is to let go of that perfection thing ... to forget about playing it "perfectly," and just play it.
It's important to acknowledge spontaneity and believe in it because, no matter how many times we practice a work, each time we play it there will be a difference.
We also need to stop thinking about that difficult place two pages ahead; our hands, feet, mind, and memory all need to be in sync with what's in progress so that what has been learned and stored in the subconscious can be accessed without interference.
Thinking about some tricky spot pages ahead of the present instant and wondering if we're going to play it correctly when we get there diverts the attention and disturbs and inhibits our ability to play in the moment of time that's unfolding and now exists.
It's important therefore to stay right with the moment.
The present moment will save us.