This is an anecdote on page 151 of Stephen King, On Writing. I found it both funny and painfully true.

If "read a lot, write a lot" is the Great Commandment -- and I assure you that it is -- how much writing constitutes a lot? That varies, of course, from writer to writer. One of my favorite stories on the subject -- probably more myth than truth -- concerns James Joyce. According to the story, a friend came to visit him one day and found the great man spawled across his writing desk in a posture of utter despair.

"James, what's wrong?" the friend asked. "Is it the work?"

Joyce indicated assent without even raising his head to look at the friend. Of course it was the work; isn't it always?

"How many words did you get today?" the friend pursued.

Joyce (still in despair, still sprawled facedown on his desk): "Seven."

"Seven? But James . . . that's good, at least for you!"

"Yes." Joyce said, finally looking up. "I suppose it is . . . but I don't know what order they go in!"