Habit. I'm telling you. I was out of the habit of writing daily. By day 5 I had to make a commitment to myself to just sit and write for one hour. Sixty torturous minutes. And whatever my word count was, that's what it would be.
Literally on the 7th day it was like old times again. I'm still trying to find the story. My characters are doing thing I didn't expect them too and stuff is happening that I hadn't planned for. It's a mess right now. But at least I'm writing. Getting something down is the hardest part. Fixing it later is a lot easier.