This is a tough one. I quit several years ago to work for myself so I know what a struggle this can be. I personally can't just sit and code for 8 hours every day. I'd go nuts. Some days I end up working much more than 8 hours if I have a lot to do and things are flowing, most I work less though.

Working from X to Y seems silly to me now. I try to set a goal of what I want to get done that day, and when it's done I'm done. The switching costs are so high when changing tasks, it rarely makes sense to start something new at the end of the day. Sometimes I work 2 hours, sometimes 10 hours, most of the time though it is between 4-6.

All that being said, I'm not accountable to a boss and a paycheck. I didn't do any work today and yet my stuff is still selling itself.