How much do you exercise a day/week?
baguasquirrel: When I was in school, I learned the real value of exercise.  When I had time to do them and still get 6 hours of sleep, I stayed healthy.  When I didn't, I'd start to feel sluggish after a week and I was prone to sickness.Doing a startup can be particularly difficult because there's nothing to force you to go out.  But the toll it will take on your mental agility will compound.You don't need an enormous amount of exercise.  I'd advocate going out and taking a walk whenever you're stuck on something.  It usually clears my head and I'll have an answer for what I was working on when I get back.