Once that's done - don't cross it. Home time is for home and should be free of the constant pull of the business. Let an answering service get the phone, don't check the emails, don't continue to work on studio "stuff" during your non-studio time. Keep home and business separate. Look forward to the weekend if you don't have a "shoot." For the sake of your sanity don't fill that precious free time with another studio project that can wait until Monday.
Sure, we all get busy and sometimes the line blurs, but constantly strive to keep the boundaries clear in your home studio. Here is one of the best articles on the subject right here at ZenHabits.net with 30 Tips on doing just that.