Flavorwire has a list: 10 of the Greatest Essays on Writing Ever Written: One that comes to my attention comes from the wonderful Donald Barthelme. His essay on “Not Knowing” includes this bit:
￼￼“The not-knowing is crucial to art, is what permits art to be made. Without the scanning process engendered by not-knowing, without the possibility of having the mind move in unanticipated directions, there would be no invention.”
The remaining essays are all wonderful, too, but I had read most of those before. Other picks: Lethem, Vonnegut, Didion, and Orwell.