I "act like" aka "pretend" that everything is being graded and everything has some sort of income/ or importance attached to it-- so "write or starve." On the second level, I work in a plodding workmanship type way to get it done.
Recently I have been getting a Master's in English Literature which I just swapped for an MFA in Fiction at another college. Each one of those assignments has a due date and will reflect on whether I can get that degree, thus get to be a college teacher in Creative Writing, or not, and also reflect on my grade point average. I have had to do awful work that I did not want to do. I have hated it every step of the way. I have written terrible final papers that I kicked and stomped into shape and which I got A's for. (MyGPA was 4.0) From all of this writers abuse, I have (I think) become something of a stone cold killer as a writer-- Or at least I hope to be. You know, an action hero-- unafraid of any stupid assignment.
I do all my assignments whether they are term papers, essays, or any other writing in the same way. I examine how it can be broken up into manageable chunks. I give myself a certain amount of time to do the work. I pre-fill the areas that I will be doing the next day so I do not start out cold. I wait for "perfection" in the final draft. Oh, and I work in the morning before I am tired. (Always get a late starting job if you work when you can). Make writing be the first thing you do not the last thing.
So how long is it to be, and when is my due-date is my motivator.
I try to do the work in 1/3rd the time I need so that I can sit down and fiddle with the wording and "poetry" during the second and third thirds. So If I tell myself that I want to write a 400-page book in one year starting in January, that means I need the rough draft by April 30th. The first draft is the rough sketch so in a 400-page novel you might have a 300-page rough draft anyway. 120 days to get 300 pages is 2.5 pages per day. You will fill that extra 100 pages later. I realize this is all mechanical stuff, but it is really motivating to know that the 3 pages per day are part of a grand scheme. During the editing parts of the year, I can slow down and relax a bit. During that time I can plan and plot another novel if I want.
Since the first draft is also the rough draft, don't sweat it if the language is basic or the scenes are sketchy. That is what it is, a sketch).
Muses. I don't believe in them. It is all just plodding ahead-- one foot in front of another with an outline as a road map. Don't wait for anything or anyone. Outline the book, section it into easy to do bits, and do it. Don't worry about whether it will be good or sell or if anyone actually likes it. Do it like work. At the end of the first 4 months, your writing will be better, and all the writing will be done, then you go back as a better writer and revise in the next 4 months, and then you go on top of that and revise again for a second revision.
Muses. I don't believe in them. In the same way that I do not believe that "praying" will make your writing any better. It is all just plodding ahead-- one foot in front of another with an outline as a road map. Don't wait for anything or anyone. Outline the book, section it into easy to do bits, and do it. Don't worry about whether it will be good or sell or if anyone actually likes it. Do it like work. At the end of the first 4 months your writing will be better, and all the writing will be done, then you go back as a better writer and revise in the next 4 months, and then you go on top of that and revise again for a second revision.