Be like a child

There are many sayings about being like a child. Jesus said once that if you cannot be like a child, you cannot enter the kingdom of God. There are many Chinese sayings that a great man is the one with a heart of a child. When I read introductions of the little prince, I found all of them praised being like a child. By which way should we be like a child? Or maybe we just whole heartedly be like a child? But as we grow, most of us cannot shake many grown men stuff, only few can do that. Is it something that we can do to be like a child, or something that only a few could attain?