Write every day. Doesn't matter what else is going on in your life - as a writer, you must write. Set a goal and stick to it, but don't overdo or you may burn out. Stop when you hit your goal, for example, 2 hours a day. It's better to write 2 hours a day than to binge write and then skip a week. Be consistent. You will be amazed at how your book will grow over time even if you write only 1/2 hour. Stop writing just before the exciting parts - gives you something to look forward to the next day.