On Being Self Critical

From a biography of Graham Greene:

There was the doubt of one's own abilities, for Darley wrote: 'You may ask could I not sustain myself on the strength of my own approbation? But it might be only my vanity, not my genius, that was strong,' and Greene stressed, 'Darley was not a man with the courage to stand against silence. Attack might have made him aggressive, silence only made him question his own powers, the most fatal act an artist can commit'.

(Thanks Catherine)