I first saw this quote on Lu's blog, Regular Ruminations (a great blog, btw, that you should totally read), and it intrigued me. So much so that I sought out the source of the quote in order to read the context.
The quote is from Madeleine L'Engle's Newberry Award Acceptance Speech in August, 1963, entitled "The Expanding Universe" and is available in full here.
It is absolutely worth reading in its entirety, but I found this bit here to be particularly brilliant.
...I took a course in college on Chaucer, one of the most explosive, imaginative, and far-reaching in influence of all writers. And I’ll never forget going to the final exam and being asked why Chaucer used certain verbal devices, certain adjectives, why he had certain characters behave in certain ways. And I wrote in a white heat of fury, “I don’t think Chaucer had any idea why he did any of these thing. That isn’t the way people write.”
I believe this as strongly now as I did then. Most of what is best in writing isn’t done deliberately.
... I heard a famous author say once that the hardest part of writing a book was making yourself sit down at the typewriter. I know what he meant. Unless a writer works constantly to improve and refine the tools of his trade they will be useless instruments if and when the moment of inspiration, of revelation, does come. This is the moment when a writer is spoken through, the moment that a writer must accept with gratitude and humility, and then attempt, as best he can, to communicate to others.
...Very few children have any problem with the world of the imagination; it’s their own world, the world of their daily life, and it’s our loss that so many of us grow out of it....