He who comes up to his own idea of greatness must always have had a very low standard of it in his mind.

Feeling that you have arrived is evidence about your standard, not about your achievement. Anyone whose sense of what is excellent keeps growing will always be behind it, because the target moves faster than the work does. Satisfaction of that final kind tends to mean the picture in your head was small enough to reach.

If you have been feeling pleased with where you have got to, go and look at the best work in your field rather than at your peers. Let the standard rise. Dissatisfaction of this sort is not self-punishment; it is simply the view from a higher shelf.