Another manifestation of my addictive personality is to do all things in excess. That includes writing. I'm enforcing a fifty-minute timer for all fiction writing to combat that instinct. All research and writing must be completed by the end of the timer. I then allow another 10 minutes to edit.
“Writing is never done, it is just due.”
-- Kelly Gallagher
After that, whatever I wrote - is finished. I may continue the story later or even reimagine it entirely, but it should never negate the doneness of the original piece.