I often sit at a desk all day and all evening. I find that these things help:
- Good chair. Height adjusted for my keyboard/mouse height. Upright back. Lumbar support. Comfortable-but-supportive seat.
- Good posture (when I remember to pay attention to it).
- Split, tented keyboard. Mechanical switches that don't require too much pressure.
- Good display. IPS panel. Light anti-glare surface. Backlight that actually dims the light source, either without pulse-width modulation, or with PWM at such high frequency that it cannot induce flicker fatigue. Brightness turned down much lower than the default. Calibrated at that brightness setting, optionally to a slightly warm color temperature.
- Muted room lighting. Nothing behind me bright enough to reflect much on the screen.
- Comfortable clothes.
- Cup of water. Regular trips to the kitchen to keep it filled.
- Frequent short breaks. Start the laundry. Get a snack. Look at objects outside. Wash a dish. Bring in the mail. Make the bed.
- Exercise. At least 10 minutes daily; preferably 30 minutes or more. Stretches. Squats. Rhythm games that require full-body movement.
The environment looks real enough. The "cats" look like weird demon creatures created by some entity that only knows dogs.