Found a guy who haven't done any hard physical labor before. You are confusing a 8-hourd hardcore shift/12 hours hard work under the boiling sun in the field with a 1-2 hour workout in a gym.
> Finally, you might be exhausted physically at the end of the day, but your mind is definitely not exhausted, which allows you to actually do something with it afterwards.
Namely, to lie down and get sleep at once.