Stephen King sits down every day and writes x amount of pages. 10 or 15 maybe, been awhile since I've read on writing but he talks about it in there. He is not super concerned about the quality of it, he just wants to get it out there. If those pages end up as part of an actual book then he'll obviously be going back over them etc. I assume Sanderson operates very similarly.

GRRM on the other hand agonizes over writing out perfect rough draft pages and thus never gets anything done.