Here's his take on when it's working -
On some days [since King's accident and recovery] writing is a pretty grim slog.
On others -- more and more of them as my leg begins to heal and my mind reaccustoms itself to its old routine -- I feel that buzz of happiness, that sense of having found the right words and put them in a line. It's like lifting off in an airplane: you're on the ground, on the ground, on the ground... and then you're up, riding on a magical cushion of air and prince of all you survey. That makes me happy, because it's what I was made to do.
And the wrapup of the book.
The rest of [the book "On Writing"] -- and perhaps the best of it -- is a permission slip: you can, you should, and if you're brave enough to start, you will. Writing is magic, as much the water of life as any other creative art. The water is free. So Drink.
Drink and be filled up.