You go through life wondering how all these people around you can be so clueless. Do they have no situational awareness? Did their parents not explain everyday manners? Do they never learn from experience? I jerked my kids back dozens of times before they learned to let people get out of an elevator before they stepped in, and I hope they retained that. But I still encounter people who want to jump in and trap me in the elevator when I'm trying to get out.
Here's one that I both complain and joke about. If a party starts at six, and I show up at seven, I'll be the only guest there until at least nine. It's even worse when you're the hostess, and your shindig starts to swing about the time you hoped it would be over.
You should go through all 24 of these social rules that clueless people break all the time and wonder at the lack of common sense (although there are a couple we could argue over). Somewhere along the way, you may come across one you didn't know about. Oops. And even if you don't, you'll start to think, maybe we all are clueless about something or other that bothers other people around us. That's a scary thought.