KNOWLEDGE.

"I've been making a list of the things they don't teach you at school. They don't teach you how to love somebody. They don't teach you how to be famous. They don't teach you how to be rich or how to be poor. They don't teach you how to walk away from someone you don't love any longer. They don't teach you how to know what's going on in someone else's mind. They don't teach you what to say to someone who's dying. They don't teach you anything worth knowing."
― Neil Gaiman