What to do you do when you sit down to play a piece and completely forget how to play it? (yes it has happened to all of us!)
Well don't get worked up - just go back to basics: Let's say we are learning 'Hot Cross Bun' :)
Starting with the first bar or first few bars:
Now learn the next 'chunk' (few bars) and then add these to the first few you learnt and so on.