I work almost every "free" hour I can, on my startup project, excepting the occassional "night off" to go to the movies or something, and the rare social outing with friends. I typically leave my day job by 6:00pm, head home, possibly stopping at Barnes & Noble for a coffee and to browse / unwind for a little while, and am home by 7:00pm. If needed, I walk across the street to Food Lion, get groceries, come home, and cook, and eat. Typically by 8pm I'm back working... on a night where I don't stop at B&N or need groceries, I'm working by 7:00 or so. I usually go until near midnight, except Friday night when I work until the wee hours of the morning. Weekend schedule is more chaotic, but I treat both days as full-fledged work-days, committed to the startup.
When I start feeling to stressed, I allow myself a night off and walk across the street to the movie theater, take in a movie, or go out to eat or something, then come home and read some light fiction or something.