A singer starts by having his instrument as a gift from God... When you have been given something in a moment of grace, it is sacrilegious to be greedy.
Not even the visionary or mystical experience ever lasts very long. It is for art to capture that experience, to offer it to, in the case of literature, its readers; to be, for a secular, materialist culture, some sort of replacement for what the love of god offers in the world of faith.
The real risks for any artist are taken in pushing the work to the limits of what is possible, in the attempt to increase the sum of what it is possible to think. Books become good when they go to this edge and risk falling over it --when they endanger the artist by reason of what he has, or has not, artistically dared.