I can code about 40 hours a week. And I mean really code, not just being at work: heads-down, super-productive hacking. All told, I spend about 32-34 hours a week at work coding so I usually end up spending about 10 hours a week on my side-project. This comes out to around 6-8 hours coding and 2-4 hours designing, researching, etc. Those numbers change quite a bit depending on overtime so I typically get in about 25 hours a month on my side-project. The thing is that I want more, but I simply cannot bring myself to code more.
It's somewhat amorphous, but I know that sometime every week I'll hit a limit. While I can keep pushing on, my productivity takes a dive. If I persist, after a week or two of overdrive, my overall performance starts to dive. I thought something was wrong with me so I took several steps to try to improve through life-hacking: I began going to a gym 3 times a week, dramatically improved my diet, and have almost entirely kicked the smoking habit (down to 2 a day from a sadly higher number). Nothing seems to work. The fatigue from ultra-focused coding just leaves my mind incapable after 40 hours of further deep concentration.
I typically spend the rest of my free time learning new things, playing games, or being with my girlfriend. I definitely enjoy these things and like to have some balance, but I feel like I'm missing that hardcore edge to really hunker down and produce a quality side-project once in a while. I feel like the hacker version of a guy who needs steroids to take it to the next level. Is this normal? Are the 16 hour/day guys the exception? Is it really that naive to try a side-project and keep the day job? Am I demanding an unreasonable amount from myself?
Thanks in advance for any feedback you guys have.