Writing something like a book takes a long time. It can't be done in one sitting. You must commit to spending weeks (months...years...) coming back again and again to the computer or pad of paper and work on that story.
How much of that story would get written if we waited for the right mood to strike us?
One piece of advice I read over and over was that one needed to commit to a schedule if one wanted to be a writer. I would have to set aside some time, at the same time every day, and spend that time writing. But this I could not do (at the time my work schedule would not permit me to write at the same time every day).
Like most writing advice, it was good in the general, but not so great in the specific. As writers, we must find what works for us, and what works for us might not be the ideal set-up for someone else.
I had to do something that would work for me. It couldn't be too much or I'd never get it done. Or, I'd get overwhelmed by the enormity of the task and I'd drop it like a New Year's resolution. Even a little writing done every day will get a novel written--it'll just take a longer time.
I started by writing a page of something, anything, every day. Some days that was garbage. But the most important thing was getting into the habit, and once I got into the habit, the habit stuck.
Nowadays, I have weekly goals. I set my goals per page (between 600 and 700 words). In a week, I aim for 12 pages or around 8000 words. I break that down into three writing sessions. (The days of being able to write everyday are gone.) Some weeks, this is easy. Others (this one, for example), this task seems nearly impossible. But I keep at it. That's all I can do.
My question of the day: What does your schedule look like?