Benjamin Franklin said long ago: "In the beginning man makes the habit. In the end, the habit makes the man."
From the standpoint of my years, I can only say that this is the wisest, most profound advice I've ever heard. If you want to live a successful life, make good habits. If you want to achieve a goal, make a habit of working toward that goal. If you want to master the guitar, then you practice chords for so many minutes each day until that practice session is second nature. If you want to be a writer, then you write so many words a day until doing so is second nature.
For a writer, work discipline is nothing more than a habit of producing work each day. Desire may get you moving toward achievement, but desire wanes in the tedium and difficulty of life. When it does, habit can take over and keep you moving to the finish line.
Create Good Habits
Creating the habit of producing pages each week is the habit successful writers need in order to reach their goal of a completed work. Develop the writing habit by producing a certain amount each day. Make that certain amount your minimum daily requirement so that you cannot rest at night if you haven't met that minimum. As you become comfortable with your habit, increase your requirement.
Desire gets you going, but habit carries you to the finish line.