In my experience, 20 hrs of project work / week is the ceiling for a solo professional. You'll need the remaining 20 hrs for a combination of new biz dev, paperwork, experimenting, and long-term planning. Once I adjusted my billable rates and expectations according - I was significantly happier & more productive.
>>> In my experience, 20 hrs of project work / week is the ceiling for a solo professional.
Same here. Also, you can't really do more than ~5hrs/d of productive work. Personally, I don't see much point in trying to pull extra few hours when I can do the same amount of work tomorrow in 1 hour or less. It hurts the income a bit but I am much much happier.