“Critics who treat 'adult' as a term of approval, instead of as a merely descriptive term, cannot be adult themselves. To be concerned about being grown up, to admire the grown up because it is grown up, to blush at the suspicion of being childish; these things are the marks of childhood and adolescence. And in childhood and adolescence they are, in moderation, healthy symptoms. Young things ought to want to grow. But to carry on into middle life or even into early manhood this concern about being adult is a mark of really arrested development. When I was ten, I read fairy tales in secret and would have been ashamed if I had been found doing so. Now that I am fifty I read them openly. When I became a man I put away childish things, including the fear of childishness and the desire to be very grown up.”
-C.S.Lewis.
Thinking about the difference between being childISH and childLIKE. And, at the core of it, those who are truly grown up are the most childlike, because they know how foolish it is to be "grown up' in the traditional sense and they know how little they really are. And the most mature know how important it is to hold on to simplicity and purity.