The day your mind stops wanting to learn about the universe and our place in it, is the day you 'die'. The rest of your life is just spent as the walking dead.
Does maturity count? Having spent 50+ years demystifying life, I don't want to "stand like curious children". I want to run like I know where the hell I'm going.
Actually, many people who grow in age and ''die'' in mind, made the ''growing old'' seem like this pathetic life of having no dreams and don't striving to achieve something great. Growing old never meant to live a pathetic life.