How much time do you spend each day on the little things? Things worth doing, but not worth writing about: checking the post office box (Is there an order? Better yet, a check?), buying socks, getting the mower fixed, driving to work?
To set realistic goals in work, any self-employed person needs to prioritize. Knowing how much (or little) time you have left can motivate you to use your time well, and to be more realistic about what you can get done.
As Randy Pausch, author of The Last Lecture, said in his excellent lecture on time management, (Pausch starts 7:30 minutes in, the lecture itself begins 12 minutes in) :
Everyone has good and bad times.
Find your creative /thinking time. Defend it ruthlessly.
Find your dead time. Schedule meetings, phone calls, and mundane stuff during it.