From a Salon.com interview with Tobias Wolff from December 2006:

Do you spend a lot of time staring at the wall or do you sit dutifully in front of a typewriter every day?

I try different things and I explore. It's like spelunking, with a light on your hat. You keep going into different chambers until you find a chamber that seems to you to be the right one; you're descending into dark and unknown territory and you can never see very far ahead.

It never gets easier, does it?

No, it gets harder in a way. It gets harder and more satisfying. Because the more you write the more you're aware of the weight of your tradition and the difficulties of the form and the more you have already done that you do not want to do again. So you're continually searching for new ways of using the story form to most perfectly contain and express the story you're telling. You're setting the bar a little higher each time to keep it interesting for yourself. There are writers who do start doing the same thing again and again and almost inevitably fall into self-parody.

[Thanks Charly!]