I worked for one month at a snack stand at a YMCA. It was the worst "job" I ever had, although it was a volunteer project. It. was. awful. I don't know how some people go in to their retail/food service jobs every single day.
I've worked at Subway and Asda (Walmart), both were horrendous and I'd never do either again if I can help it. Your perspective of the general public changes completely when you start working in retail/fast food, and not for the best either.