Like other people have pointed out, it all depends what you're selling. If you're trying to sell people something you don't believe in and they don't want, that would be soul crushing. But if the opposite is true, it could actually be enjoyable (provided you're the type of person who's a good salesman) In high school I worked on commission at retail stores selling sneakers and track pants and stuff like that. I was one of those kids with the attitude of "just buy something expensive, I really don't care why" so obviously I did pretty crappy in terms of commissions.
In first year university I became a cashier at Zellers (like a Canadian K-Mart.) The pay was crappy, but that was pretty easy. The only hassle was I always got in trouble for not going through this whole routine of "do you want to put this on your Zellers credit card? Do you want to use you zellers rewards card? do you want to sign up for a zellers credit card? Do you want to sign up for a zellers rewards card? (if they say no to everything, tell them how many zellers points the COULD have earned)." for every single customer, even if they were buying just a can of coke.