According to Susan Neiman, the most important distinction in the world is the difference between what is and what ought to be. Recognizing that distinction is central to the process of growing up. (Why Grow Up?: Subversive Thoughts for an Infantile Age)
You need not be Peter Pan to feel uneasy about the prospect of becoming adult. Indeed, it’s easy to argue that Peter Pan, most drastically imitated by Michael Jackson, is an emblem of our times. Being grown-up is widely considered to be a matter of renouncing your hopes and dreams, accepting the limits of the reality you are given, and resigning yourself to a life that will be less adventurous, worthwhile and significant than you supposed when you began it.