So we realize that we must accept the historical event as the truth.  We have to receive this Child as a personal gift to us.  But we also need to be changed as a result.
As a child you believe what adults say and tell you, but as we grow up we expect our children to question and decide for themselves on everything they hear.  We move from belief to rational explanation.  But when we receive THE CHILD, something needs to change!

Matthew 18:2-4 And He (Jesus) called a little child to Himself and put him in the midst of them, 3 And said, Truly I say to you, unless you repent (change, turn about) and become like little children [trusting, lowly – humble, loving, forgiving], you can never enter the kingdom of heaven [at all]. 4 Whoever will humble himself therefore and become like this little child [trusting, lowly, loving, forgiving] is greatest in the kingdom of heaven.

We must become like a child.    This is so foreign to human nature and what society tells us.  There is a difference between being childlike and childish.
To be childish means to be immature, simple/silly, befitting a child.

1 Corinthians 13:11 When I was a child, I spoke as a child, I understood as a child, I thought as a child; but when I became a man, I put away childish things.

Being childlike is having the qualities of a child, innocent, trust, humble, loving and forgiving, teachable, obedient and willing to do his father’s will.