Yeah.. I edit/write in a constant iterative fashion. It helps me to keep all my threads, and not forget things I left pages behind. Works for me, but it is not for all.
On HUGE thing that helps me (and from what I understand, most authors) is READ, READ, READ, and occasionally catch a movie, then read some more.
Finally, as GMW said, sometimes you just have to write. Get words on the paper and fight through it. Who cares if you trash it all later, just write something. It is like exercising in a way. The more you fight through it the better you get at it.