Nothing provides motivation to write (or revise) better than a looming deadline when your publisher has already paid you your advance.
However, for those of you whose deadlines are looming only in their minds, the resulting motivation may be, shall we say, less urgently experienced.
Accountability is of course a blessing and a curse, but when you want to get something done, if you create a system for accountability you dramatically increase the probability that you'll get it done.
Why?
Because you'll be mortified if you don't.
A writing partner who is currently writing something is ideal, as you can set goals together and your processes might be similar. I recommend weekly goals for, say, 90 days. You should speak or e-mail once a week, and report what you have done to your partner and even give them something to read and comment on (it hurts, I know). This way, you have someone to talk to about your writing and your struggles, and that someone can even give you feedback if you want it (sometimes you won't. Instead, you'll simply want a congratulations for doing what you were supposed to do.).
Not everyone is surrounded by writers, however. Or maybe the writers you know aren't people you'd feel comfortable going on a 90-day journey with. If that's the case, who in your life--whom you trust and wouldn't mind speaking with once a week--is either working on a project or hasn't started a project they've always dreamed of (i.e., their "someday" never arrived). Ask that person if he wants to get down to business and explain how you can help each other with your goals by being accountable to each other.
Create a spreadsheet with deadlines, actions to take, goals to be reached, and even your feelings during the process, for the entire 90 days (or maybe just 30 days--whatever time period works best for both of you). Make two copies: one for you and one for your partner. Once a week, talk about what you've done and how you felt. A regular set of topics will likely emerge in your conversations, which will end up being like therapy: who is supportive of your work, who resents the time you spend on it, where you get your best work done, when you get your best work done, how you feel about being accountable.
You might revise your schedule based on how things go during the first week or two. Many people find they were unrealistic when they created the schedule, not factoring in all of the vicissitudes of daily life that keep them from their plans.
Finally, remember to give yourself something wonderful upon reaching your goal. Do something fun with your partner--celebrate your accomplishments!
And then set some new goals and begin again . . .