In men of genius, sterile years precede productive years, these again to be followed by sterility, the barren periods being marked by psychological self-depreciation, by the feeling that they are less than other men; times in which the remembrance of the creative periods is a torment, and when they envy those who go about undisturbed by such penalties. Just as his moments of ecstasy are more poignant, so are the periods of depression of a man of genius more intense than those of other men [Wie seine Ekstasen gewaltiger sind als die der anderen, so sind auch seine Depressionen fürchterlicher]. Every great man has such periods, of longer or shorter duration, times in which he loses self-confidence, ... times in which, indeed, he may be sowing the seeds of a future harvest, but which are devoid of the stimulus to production.