From the diary of André Gide, on December 31, 1891:

When one has begun to write, the hardest thing is to be sincere. Essential to mull over that idea and to define artistic sincerity. Meanwhile, I hit upon this: the word must never precede the idea. Or else: the word must always be necessitated by the idea. It must be irresistible and inevitable; and the same is true of the sentence, of the whole work of art. And for the artist's whole life, since his vocation must be irresistible. He must be incapable of not writing (I should prefer him to resist himself in the beginning and to suffer therefore).

The fear of not being sincere has been tormenting me for several months and preventing me from writing. Oh, to be utterly and perfectly sincere…

In The Journals of André Gide, translated by Justin O’Brien.