The lessons in humility in the Chekhov chapter are particularly useful, coming nearer the point than I did when I tried to describe the importance of forgiveness in David Foster Wallace's work. Here's Prose quoting Chekhov:
It is time for writers to admit that nothing in this world makes sense. Only fools and charlatans think they know and understand everything. The stupider they are, the wider they conceive their horizons to be. And if an artist decides to declare that he understands nothing of what he sees--this in itself constitutes a considerable clarity in the realm of thought, and a great step forward.
I love this. It's so easy to fall into the trap of believing there to be a list of prerequisites for being a writer, of regarding Tolstoy and Joyce and the other greats with such veneration that we forget that they, too, were simply humans who told stories--that their ways with words would be nothing if not for the peculiar honesty of their visions. Their truths are less pronounced than admitted.
The heart of the matter was expressed more pithily by Howard Nemerov, who told a self-described aspiring writer, "Okay, so write something."
It's amusing that the advice doesn't change at the pot-boiler end of the spectrum. Peter O'Donnell, author of the Modesty Blaise comic strip and the Madeleine Brent novels, recounts a conversation with a pitiless editor: "You're supposed to be an author, aren't you? Well f--- off and auth."