Joe has a good post on how he keeps writing, and the struggles he had in it. For him a piece of software, Ulysses, worked to help him track stats and keep on his goal of writing.
I schedule time for "production" daily after I read for an hour I have an hour to produce something. At one point it was only writing. Now it's sometimes writing, sometimes editing videos and getting them ready to put on YouTube.
For my upcoming book (subscribe to hear about it first) I schedule Friday afternoon to work on the book for 2 - 3 hours. It's still in research/planning so I'm doing that work then. Eventually (maybe this week) it will be in writing stage so I'll write.