I went through a similar period too. Turned out to be burn out. It really does creep up on you. Doing a startup work and studying EE is probably too much. I

I went through a similar period too. Turned out to be burn out. It really does creep up on you. Doing a startup work and studying EE is probably too much. In my case it was a day job, moonlighting at a startup and a part-time Masters in software engineering. Hope your girlfriend is making you have some quality down time. If she is high maintenance, then .... ;-) My solution was to simplify my life, cut back on TV and take up meditation, ditch the Masters and the startup and build a career and a social life. Your stress levels go way down when you finally learn not sweat over all the materialistic desires. Personally I'm wary of supplements, healthy eating is a simpler and more reliable strategy.