I can wholeheartedly agree with this. I do Web Development for a living, so I write a lot off business application backend / frontend JS code. While it's certainly fun (especially when there's no pre-built solution for some problems and you have to wrap up your own code to fill the gap), most of my personal code revolves about making computer games.

These end up for the most part being some multiplayer HTML5 Tech Demos (where I can play with all the fancy new Web Tech I can't use at my day job) or really old-school stuff like doing Z80 Assembly for my very own old-school Nintendo GameBoy Jump & Run (along side with a custom assembler / compiler and toolchain) and digging in dissamblies of commercial games.

I can't imaging just doing "work" code, because that can be very exhausting at times. But I certainly have no problem staying up all night and getting that game up and running around 5AM in the morning just to scribble down some more ideas before I finally head off to bed.

I have tried starting a few side projects that are completely different from my day job, but the scattered hours that I get to work on them makes it twice as hard to get anywhere with them.

Now my side project is based on the database I have built at work (as an in house project). It makes it so much easier, as the hard non-coding problems are usually well understood, as I have thought about them before. I can pick it up and leave it without forgetting anywhere near as much. And it gets rid of the frustration I have at work, because the quality of the code is always ignored in favor of new feature that were needed yesterday. Same thing but with nicely written code.

> I think the key is, write different kinds of code for your job and for your hobby.

I would expand this to say (just on personal experience) also have varied hobbies. They then challenge you in completely different ways allowing the exercise of one activity to be downtime from the others.