I worked for myself for about a decade (web dev) and always considered getting 6 billable hours in a good day.
working when you feel like you can contribute, billing exactly those hours, and filling the rest of your time with activities of your choice feels very honest and liberating.
if i feel like i can't get things done because of the environment then i don't work, and i don't bill. if i finish a job and they have no more work for me then i say, thanks, keep me in mind, let me know if you have any problems.
not really a capitalist, but the transactional nature removes all the festering emotional complications. and you can be a lot more straightforward about where things are broken.