I was going to comment on this. As someone going through it now (working for money in the morning, and working on craft in the nights,) it seems that many of my peers who do the same thing are burning out because they charge on until 2-3am, and get up for work at 6-7am.
You aren't going anywhere faster because you work yourself to death. A solid 3-4 hours at night, some great sleep, and I'm good to go. I just expect the payoff (of working on the craft) to come much, much slower than if it were my full time gig.
It works for me, and I take plenty of breaks from working at night because girlfriend, friends, and family would all leave if I didn't. I just take it slow and steady.
On the other hand, it's easy to become complacent and lose motivation to keep toiling away. Maintaining a steady regimen of working, even just a little, each night seems to be the best way to not lose interest. Otherwise it's easy to continually say to yourself "well, I'll work on it tomorrow" for the hundredth time in a row.
Thanks for your comment. I really appreciate it.