Flannery O'Connor, writing to a friend ("A") about recent criticism the friend had received concerning a book she had written, and the subsequent depression she had fallen into:
No matter how just the criticism, any criticism at all which depresses you to the extent that you feel you cannot ever write anything worth anything is from the Devil and to subject yourself to it is for you an occasion of sin. In you, the talent is there and you are expected to use it. Whether the work itself is completely successful, or whether you ever get any worldly success out of it, is a matter of no concern to you. It is like the Japanese swordsmen who are indifferent to getting slain in the duel. ... The human comes before art. You do not write the best you can for the sake of art but for the sake of returning your talent increased to the invisible God to use or not use as he sees fit. Resignation to the will of God does not mean that you stop resisting evil or obstacles, it means that you leave the outcome out of your personal considerations. It is the most concern coupled with the least concern.
(Habit of Being: Letters of Flannery O'Connor, 25 November 1960.)
And elsewhere, a favorite:
Sit at yr machine.
(Habit of Being: Letters of Flannery O'Connor, to Cecil Dawkins, 11 July 1960.)