Sometimes we internalize what goes on in other people's heads. This is definitely not a useful way to spend our time. If you own a circus, then the monkeys in it are your responsibility. But if it's not your circus, then those ain't your monkeys to worry about.
If you walk into the post office, and the guy behind the counter grimaces at you before you even say anything, that's because of the circus going on inside his head. Those monkeys were already bouncing around, throwing feces, and stealing people's keys before you walked in the door. You didn't bring the monkeys, he did. Leave them in there when you go.
If you have a first date with a girl and she starts crying when you drop her off at home because she doesn't want you to leave, that's because she's got her own monkeys that smear bananas on her walls, and tell her she can't survive alone. Not your monkeys.
If your neighbor has a highlighter-huffing addiction, and you go to his apartment every day to throw out highlighters, and you're up all night wondering, "Why does he huff highlighters?" That's because of the highlighter-huffing monkeys inside his head.
This is not your circus. These are not your monkeys.
There's a useful saying in Al-Anon (the organization formed to help the family members of alcoholics) that goes: "I didn’t cause it, I can’t control it, and I can’t cure it."
People are going to have feelings, and irrational behaviors, and it's due to the circus in their own heads. You are not responsible for their hatefulness at customers, their sadness at the end of a date, or their need to huff highlighters. Sure, sometimes we're totally responsible for hurting another person, but as long as you didn't wrong them, then it's their circus. You are only responsible for keeping your side of the street clean.
Internalizing other people's damaged reactions gets into my stomach and makes me feel sick. It's like a poison that can put me out of commission. I want to live free from the feelings that I somehow caused it, can control it, or can cure it. And I want to be free to be creative and useful to my friends, family, and my community.
Also, monkeys will throw shit at you.