As I’ve studied happiness and human nature, I’ve become more and more struck by how we each live in our own world—shaped by our own experiences, our own nature, our own interests, our own values. We all have our own perspective.

As writer Zora Neale Hurston observed, “Every man’s spice-box seasons his own food.”

I love collecting examples where I see this phenomenon in action.

For instance, with medication, sometimes one person’s negative side effect is the very reason that someone else takes that medication. I have a cat allergy, but I don’t like taking certain kinds of antihistamines, because they make me feel so sleepy. And other people take those antihistamines, because they want to feel sleepy, they don’t care about the effect on allergies. One person’s reason for taking medication is another person’s negative side effect.

I was in a crowded park once, and I saw a little girl start talking to a squirrel that had come near her. A passer-by also stopped, and he said kindly to the girl, “Oh honey, I don’t think that squirrel speaks Spanish.” But of course that squirrel speaks Spanish just as well as English—or any other language!

And then there’s the old story where a traveler is standing on the side of a river, and he’s desperate to get across. He sees a man standing on the far bank, and shouts, “Quick, tell me, how do I get to the other side of the river?” The man pauses and looks puzzled by the question. So the traveler yells again, “Please, please, can you tell me, how do I get to the other side of the river.” And the man answers, “Mister, you are on the other side of the river.”

It’s easy to forget that the way we see the world is very much shaped by our own perspective.