Suppose you are in a relationship and you want to be exclusive. Why? (Let's assume there is no risk of STDs or unintended pregnancies.) Suppose your partner checks out someone else. Do you feel a pang of jealousy? If so, what exactly goes through your mind in that fleeting moment?
I don't know. I've never been in a relationship, and have no intuitions about how whether or why I would want to be exclusive, or how I would react if she checks out someone else.
Sometimes our minds suddenly "click" and we see a topic in a new light. Or sometimes we think we understand an idea, think it's stupid and ignore attempts to explain it ("yeah, I already know that"), until we suddenly realize that our understanding was wrong.
This kind of insight is supposedly hard to transmit, but it might be worth a try!
So, what kind of important and valuable insights do you wish you had earlier? Could you try to explain briefly what led to the insight, in a way that might help others get it?