Problem is...when do you write? When do you pound out another 350+ page book? When do you block out the chapters? When do you do your research?
Writing to be published, not for a hobby, is a job. A full time job. You have to commit hours to it. Whether it's during your kid's naptime, after work, or during your beloved television show...you have to put in the hours at the computer to make any real progress.
An agent once told me that writers under contract are expected to produce a book every 4-6 months. Months, people, from research to revisions. Whew! Sounds daunting...but it can be done, is done regularly by authors everyday. The way to do that is to have a schedule. An iron-clad, cannot-alter, leave-me-to-do-my-work schedule. And you have to commit to it.