Jacques Barzun in A Writer’s Discipline:
[We] transfer a part of our intellectual and emotional insides into an independent and self-sustaining outside [when we write]. It follows that if we have any doubts about the strength, truth, or beauty of our insides, the doubt acts as an automatic censor which quietly forbids the act of exhibition.
I will add, too (and it is probably a measure of defensiveness that makes me say so), that the lack of those doubts is very easy to see as arrogance, and that is profoundly disappointing to me.
Surely there must be a balanced place we may live without either fear or pride:
You will keep in perfect peace the mind [that is] dependent [on You],
for it is trusting in You.
Isaiah 26:3