From Mark Childress's hilarious and oh-so-true essay, "Fear of Finishing," in Writers Workshop in a Book: The Squaw Valley Community of Writers on the Art of Fiction (2007):
"Of course, the moment when a book is best comes before you have written a word of it. Let me repeat, a book is at its absolute best--and will never be better--than when it is unwritten. When it's only an idea. A shiny beautiful thing twisting and dangling in midair. A concept, a notion, a radical reinvention of the very idea of the novel. A shade, an arc, a passage of time . . . a big swath of pages easily written, in the naive and simpleminded imagination of the novelist imagining himself in the act of writing it.
After that, it only gets worse. Every page you write is in some ways a tiny death . . . of the illusion with which you began. Every clumsy, unstructured, redundant sentence that you apply to paper is one less deathless, tripping, dancing, rhythmical internally rhyming piece of brilliance like that you had in mind when you sat down at the piano and started to play." (191-192)
Thank God for ear-plugs.