This thread already has some great advice for productivity and time management and there's nothing I could add on top of this. I'm pretty sure you will be able to cut out some time for game development using some of these tricks. Skimming this thread, most of the postings deal with how to get more work done and how to squeeze in some little tasks into every slightly available corner of your day - and I guess, this is what you asked for.
Now I'm not sure how everyone else is in this regard, but for me personally, there always has been a hidden danger in all this. I've started developing hobby projects when I was twelve, like a lot of programmers do, and I sometimes poured every waking hour into it. Motivation was not the problem most of the time - rather, it was
settling down and stopping. Sometimes I would be on vacation with my family and become totally stressed out of this one problem I wasn't able to solve back home, and I simply couldn't let go. Some other times, I would do nothing but work for a week straight. I still do this sometimes, and my experience is that it wears you out.
It feels great at first, because you're getting things done, you're making progress! Yeah sure, you get a little tired and have less time for social life and enjoying stuff like reading or watching movies, but whatever, just look at how much you've managed to do, right? For a short period of time, this is awesome. But if you're like me, there is always the danger that this is not a short period of time, but slowly becomes the norm for a while. And that can bring you down.
Besides all the work, remember relaxing and doing things you love, and do spend time with friends and family. This really shouldn't be the last point on your ToDo.
Sometimes the most important part of your work is to know when to stop. Learn to watch yourself.
I currently have two jobs at once, and am studying towards my masters degree - a combined theoretical effort of seven point five days a week. And
then there is that medium-big Open Source project I'm managing, tech support for its small community and my blog to update. That's quite a lot to do, but I still chose to do it all the time, because it's challenging, rewarding and sometimes even fun. I still fall into the workaholic-trap from time to time, and luckily there is friends, family and relationship to stop me. I'm slowly learning to do so myself.
So, I guess what I'm trying to say is, be careful. That is all