Can it be done? and, Can I do it?

Writing every book, the writer must solve two problems: Can it be done? and, Can I do it? Every book has an intrinsic impossibility, which its writer discovers as soon as his first excitement dwindles. The problem is structural; it is insoluble; it is why no one can ever write this book. Complex stories, essays, and poems have this problem, too – the prohibitive structural defect the writer wishes he had never noticed. He writes it in spite of that. He finds ways to minimize the difficulty; he strengthens other virtues; he cantilevers the whole narrative out into thin air, and it holds. And if it can be done, then he can do it, and only he. For there is nothing in the material for this book that suggests to anyone but him alone its possibilities for meaning and feeling. 

from “The Writing Life” by Annie Dillard