While some writers have deadlines set by their editor or publishing house, there are many writers who do not have specific deadlines to meet. For those without deadlines, there isn't the stress of getting a project done. For them, it's a freedom of sorts! Freedom to do whatever one wants, including write.
But when was the last time you had a full eight-hour day to write? How did you spend it? Did you spend all eight hours writing? Did you spend seven hours writing? Or did you look at the clock, see that you had eight more hours, so why not call your mom and catch up, do some laundry, or clean off your desk?
Do you find yourself wasting more time when you have a full day available, or when you only have two or three hours to write? If you're like most people, you'll waste away a good day, because you don't have any deadlines to meet. So why not set some for yourself?
Look at your calendar, and look at your project list. Perhaps you have a novel you are working on, which is about half-way written. And your calendar says you have three months until family vacation.
Wouldn't it be nice to go on vacation with that novel under your belt? How can you enjoy yourself when you know you have a huge project waiting for you at home?
Work out the next three months, planning time to write every week. For instance, if you have 150 pages to write to finish the book, and you want to get it done in ten weeks, giving yourself two weeks to pack, that means you have to write fifteen pages every week to meet your self-imposed deadline. Then sit down and write, tracking your pages as you go.
This method may not work for everyone. Some people can't take their own deadlines seriously, because they are not accountable to anyone. So either make yourself accountable (to a writing buddy or spouse, perhaps), or use the reward system instead. Tell yourself that for every 50 pages you complete, you can buy yourself a new book or indulge in a pint of your favorite gourmet ice cream. Use a reward that means something special to you.
By making yourself disciplined, you will be more productive. And being more productive makes you more money.