Imagine that every adult in the world was assigned a random fifteen-year-old who got to make all their decisions for them. That fifteen-year-old could follow you around, decide what you wear every day, choose who you're in a relationship with and what career you have, pick your tattoos, and tell you what your life's grand ambitions are.
Wild idea, right? Nothing against fifteen-year-olds (the ones I know are all pretty rad actually), but a world made up only of fifteen-year-olds and the choices they make would be an odd one indeed. It would certainly be a more interesting world. There'd be more wannabe rockstars and fewer accountants, that's for sure, and a lot more people tripping on their wildly oversized pants.
But, in a way, there is a fifteen-year-old who makes a lot of decisions for you. Except, instead of a random teen assigned to you, there's a specific one: the person you were when you were younger.