Have you tried working when you feel like it (or when you really have to), and just not working when you're not in the mood? I had a three year period working freelance and it was most profitable and fun. I have no clue how many hours I was doing but for the last six months I only worked a few hours a week because I was able to automate most of my work.

I'm doing a startup now and this lifestyle wouldn't be acceptable to my partners so it's back to a 9-late schedule plus weekends. I'm nowhere near as productive and strongly feel like I'm accomplishing less, but to go back to working how I like would just cause conflicts.