There is a saying in Russian: "Wanted to improve, ended up as always" 
Russians, probably northeastern Italians too, are quite pragmatic if not totally philosophical in accepting their limitations. Trying to improve is sometimes part of trying to stay as good as one thought one might have been. Which unfortunately becomes a subjective call on an objective thought as enshrined in surviving works that may or may not bolster the soul from doubt. I think all people within creative processes feel moments of uncertainty. They would have to, or be too wrapped up within themselves to know what the world outside was capable of achieving and, hence, their relative position within it.
To make matters worse, there are times when pressure and/or volume of work remove, if temporarily, the power to distinguish between good, okay or excellent (hoping, of course, that purely good technique will have avoided the category of lousy!).
And that's a real difficulty, because too much concern with externals reduces the power of one's convictions, and should they weaken, you are lost. I know beyond doubt that had the young me had the doubts of old me, old me wouldn't be today where he finds himself. Ignorance being bliss, or dedication winning out? It depends, really, on whether one is advising or being the one doing the doing.
Rob
