But the material of experience is not the material of expression and I think the distress you feel, as a writer, comes from a tendency on your part to assimilate the two. The issue is roughly that raised by Proust in his campaign against naturalism and the distinction he made between the “real” of the human predicament and the artist’s “ideal real” remains certainly valid for me and indeed badly in need of revival. I understand, I think no one better, the flight from experience to expression and I understand the necessary failure of both. But it is the flight from one order or disorder to an order or disorder of a different nature and the two failures are essentially dissimilar in kind. Thus failure in life can hardly be anything but dismal at the best, whereas there is nothing more exciting for the writer, or richer in unexploited expressive possibilities, than the failure to express.
— Beckett, from a letter to a fellow writer (via here)