The blurry line between childhood and adulthood is an important one to explore in your stories and when creating your characters. Just about everyone has a moment when they started to feel like an adult. Did it take a death in the family? A realization that your parents weren't invincible? The fall of a hero of yours? Or discovering in adequacies in yourself? A "grown-up moment" is often a fall from bliss, but it usually leaves us wiser and with a clearer vision of how the world works. It is a hopeful moment, to me; when a veil is lifted from our eyes, we're freer to understand and grow.