Have been discussing this very subject at the club the other day. I usually have quite long spells of good progress and consistency, and then occasionally have a "stinker" of a day. I think it is recognising these "off days" which makes you a better/safer pilot......its when you dont recognise them you should be worrying. Im only a 180 hr PPL .....it would be nice to know whether the experienced APTL have these "off days" too.