It's really only a piece of a quote.

Here's the other piece, which also does a pretty good job pretending to be a full quote:

I am not especially satisfied with my own imaginative works, my fiction. I am simply impressed by the unexpected insights which shower down on me when my job is to imagine, as contrasted with the woodenly familiar ideas which clutter my desk when my job is to tell the truth.

I guess it's time to start writing fiction.