When I was a teenager, I was a little asshole to fast food and phone tech-support workers (basically falling into the "Karen" stereotype of people). I feel pretty bad about that now, because of course these people don't make nearly enough to put up with me being a douchebag to them. It's entirely possible that I ruined at least a few people's day by being a dick, for no other reason than I was unwilling to realize that people making minimum wage really shouldn't be yelled at unless they're mean first (which they generally aren't).
Nowadays I try and be extremely polite to people serving me food or checking me out at the grocery store, and make a point to only be mean to people whose job it is to be yelled at.