What defines a child? Someone who still has physical and mental growth left to do. I believe what keeps us young as full grown humans is keeping that childlike questioning. Many problems in the world like racism, depression etc continue on because people don't ask why they feel the way they do and attempt to change it. Instead they accept things as they are and appear. Everyone should always be growing mentally / spiritually (or whatever term you wish to apply to the ethereal portion of our being) and asking questions is a large part of the key.
Question everything, observe and analyze. That is the only way you are going to improve your life and the world around you. Why? Because there is still a lot to be discovered in the universe and who better to find the answers than you.