I could be driving ahead of you one day, too slow for your preferences and, me being a stranger, you may peg me permanently as the person who drives too slow. You don't stop to think that I woke up later than usual for work this morning because I didn't get enough sleep from writing an essay I procrastinated until today and now, due to my drowsiness, I'm driving a little bit more slowly than I typically would because I don't want to preemptively stress myself out before I even get to the work I'm already late to. Why would you? You have no control over that, and you have no invested interest in seeing that my day runs smoothly. Bad analogy, I know, especially since I don't drive, but the detail is what I'm getting at.
This is called a sonder: "the realization that each random passerby is living a life as vivid and complex as your own—populated with their own ambitions, friends, routines, worries and inherited craziness—an epic story that continues invisibly around you like an anthill sprawling deep underground, with elaborate passageways to thousands of other lives that you’ll never know existed, in which you might appear only once, as an extra sipping coffee in the background, as a blur of traffic passing on the highway, as a lighted window at dusk."
And so I ask not that you go about your day ignoring everyone you meet. Trust me, pretty much everybody you meet working at the grocery store today could be happier. Nobody wants to work minimum wage. So I want you to exercise a little sympathy for those around you.
I'll give you another example. If you and another person are walking towards another and can't pass side by side, there are two things you can do. One, you can push past the other person and be about your day. They will rightly consider you rude and have predominantly negative thoughts for the next few moments. Or, you can stop, let them past, and the worst that can happen is that both parties come out neutral in the exchange. More likely, though, you could make eye contact, share genuine smiles, and a simple "Thank you" would lighten your day up a little bit. You have no positive benefit of pushing past that person, but you do come out on top if you are willing to be a little patient. Because who knows? Maybe your act of kindness will lead them to be more patient the next time somebody needs to pass them.
I hope you have a wonderful day. Now go make it happen through kindness and patience.