Mary Stella wrote in comments: Right now, my biggest conflict with writing and selling books is how to balance all the aspects of the business with my life and day job. So much to do with marketing and promotion on top of writing -- so little time to do it!
I admire writers who work in publishing and hold down a day job. Writing full-time is something we all aspire to, but in reality, it can't be done (unless you're a wealthy childless orphan living in a plastic bubble are surrounded by lots of trustworthy servants.)
Even if you don't have a day job, you've got a life that probably includes a spouse or significant other, children, a home, extended family, friends, and/or pets. At some point, no matter how understanding they are, the people in your life need your attention.
Balancing writing with your day job and your life requires very creative time management, but you first need to know how well you're using your time. Put on a watch and slip a little notebook and pen in your pocket, and go about doing what you usually do every day, only write down what it is and how much time you spend on it. Repeat for an entire week, then tally up your activities and hours.
You should have time listed very day when you were writing or working on writing-related projects. If you didn't write, look at what you actually did that day. What would you be willing to trade off for some writing time? Twenty hours a week watching television, talking on the phone for social reasons, playing video games or cruising the internet could be turned into 5,000-10,000 words in new material.
Be sensitive to your creative rhythms during the day, too. I always thought I was a night person (I'm not.) I doubled my productivity by switching from being a mainly evening-nighttime writer to predawn writer. It was hard to get used to beginning my day at 5 am, but I found out that I write better and faster early in the morning while I'm more in the mood to do editing and other projects at night.
Don't try to go the all-work, no-play route; you'll likely burn out. No matter how busy I am, every day I take an hour to paint, quilt, listen to music, walk or do something else that makes me feel relaxed and happy.
If you've found something that better manages your time and/or boosts your productivity, let us know in comments.