40 hours a week is a long time to do something. Anything, really. Except maybe sleep, which is the exception to a lot of rules.
My question is this: is it easier to work a backbreaking job or an office job for 8 hours a day?
My answer: a backbreaking job. At least when you come home, you feel like you've earned a break. And people give you sympathy. If you're working an office job, what have you honestly been doing all day to make you so tired?