What drains your energy? What forces you to the reserve tank? Make a list of everything you do in a week—laundry, social engagements, neighborhood stuff, family commitments, sports, reading. Which events—even if they are intense or taxing in some way—leave you energized, fed? Which make you feel antsy, needy, bored, or just slightly frustrated? Which have "shoulds" attached to them? Which do you engage in freely, not because anyone is "watching" or "expecting" it of you?
Circle the activities or people or situations that drain you more than they feed you. Make a radical scary promise to stay away from those activities. You're writing a book. You can't do such a difficult thing on an empty tank.
Make a second list of activities that take up creative parts of you. Talking with your girlfriends at lunch. Jogging through the dunes with Charlie, your spaniel. Working at the soup kitchen. Teaching. It is likely going to be hard to give up these activities because they are so fulfilling, they are feeding the creative you. Look at the list honestly. Is there enough of your creative energy left over for a book? Do the math.