You were taught about five senses in school. Sight, hearing, smell, taste, touch. Maybe you got a bonus lesson on proprioception, which is the sense of where your body is in space, like knowing your arm is raised even when your eyes are closed. And maybe, if you were lucky, someone mentioned vestibular sense, which is balance and movement through space. But interoception? Almost nobody learns about interoception in school. And it might be the most important one.