Today I read a nice little book by William Germano called From Dissertation to Book. Even if you are not at the book phase, his commentary on setting your own writing schedule might resonate with you.
"It would be nice to have someone checking in one you every day, just to see you got through the five pages you promised yourself you would redraft by dinnertime. But even if you live with someone else, it's unlikely you want to jeopardize the peace of your domestic unit by placing that responsibility on another person's shoulders. The job is yours, and the timetable has to be yours, too-yours to sketch out, and yours to police"
Germano nails it! This feels true everyday and success yesterday does not mean success today.
Every day is a new challenge -- you must wrangle the alligator (yourself) into the chair. I find it easier to do in the am...I have heard it said that we have just a teaspoon of discipline a day. Use it on your writing.
Good luck...I'll be at it again tomorrow am...and tonight if I can get myself settled down again.