While the 8 hrs of just about any manual labor job is much more work than 8 hrs at school, at least you don't have to worry about it when you go home.
I worked several manual labor jobs during summer breaks in high school, and the freedom to think about whatever you wanted at night (instead of homework or activities) was at least mentally liberating, even if I was dead tired from moving boxes of tomatoes all day.
Yeah, wait until you're older and have a corp desk job. The days spent toiling moving furniture will feel like your past life as a greek god. You'll look back on stuffing any food you want into a naturally evolving muscular machine of a body as your ass slowly forms into a chair shape around the dent of your paid for yet unused Snap-Fitness card.
Can you not go out for walks at your corp desk job? Every one I've had didn't have a problem if you left the office for ~20 minutes mid-afternoon to get out and stretch. Some would even have self-organized games of soccer or volleyball to break up the monotony.
Unless you're operating dangerous machinery, you don't need as much sleep to work effectively at a warehouse. 6-7 hours and to recover physically and then a couple days off every so often to rest and you'll be fine. You don't have to think much, you just have to be strong and willing to exert effort.
Plus, getting to sleep at night when working a warehouse job is pretty easy, you're usually exhausted when you get home and have nothing to do but eat and sleep.
It's much different than a technical job that requires focus, concentration, inspiration, and mental discipline. Much different from work that requires social interaction with people. The mental states associated with lack of sleep can be disastrous in those environments.
