People do not really grow up they remain kids all of their life. However, people do hide the fact that they have these tendencies. The reason why they hide these tendencies is because the world wants us to act like adults. Acting like adults however is boring and most adults will tell you that the best time of their life was when they were a kid.
Being a kid means that you can enjoy all of the cool kiddy stuff, toys and games and adventures that kids have. Therefore, if you are an adult take the time to enjoy yourself as a kid every once in a while.