Ask HN: How do you avoid screen fatigue?

I am a developer clocking in 10-11 hours a day (9-7). I take a 1.5 hour lunch break at noon for the gym and then another 15 min break around 4:30, yet I code for the rest of the time (or at least sit in front of the screen). I avoid simple carbs, choose whole foods, and drink a lot of water - enough to make me go to the bathroom every 1.5 hrs or so (nice way to force me to stand up and walk). I also get around 7-8:30hrs of sleep a night to avoid zombying around, and drink max one shot of espresso always before noon. I am in my late 20s.

I find that, at the end of nearly 90% of days, my eyes hurt a lot (I have 20/20 vision thank the gnu gods), I have pounding headaches, and my mood plummets, making me an unpleasant fella.

None of my colleagues have the same problem, or at least they tell me they don’t. They take less breaks, don’t exercise, and eat oreos and twixes for breakfast, lunch, and dinner, on top of three or so cans of diet coke daily (of course, not everyone does this, but some do and still none have this problem).

Evidently, this makes me upset. Have you experienced the same and been able to improve the situation? If so, how?