When Jesus said that only those who were like little children would enter heaven, he was referring to innocence and non judgment. Judgment is the biggest attribute of the ego. When we judge, we cannot see the Unity of all that is. If you come from judgment, come from the ego, you will not "see" heaven. Heaven is within, but our judgment cuts us off from recognizing this. When we judge others, we are really judging ourself. We are not to become like little children in a physical state but rather our mental state. When we see from unity, we see with wonder, innocence, gratitude, and awe. These are attributes of how a child looks at the world until they are "taught" by adults to judge and to see the world as a harsh or evil place. Each of us can return to that innocence and that wonder, opening the doors of heaven.