Paul tells us about Jesus Christ, the incarnate Godman, that all things have been created through him and for him (Col 1.16). Therefore, the moment when Christ comes into the world is the culmination of the history of the created order. Now, the proper inheritor and owner of all things has arrived, the true King of kings, to receive what is rightly his.
At the scene of his birth, the ox and the ass look upon him. They recognize their master (Is 1.3). The angels sing, because God has declared peace on earth on the people whom he favors. The blessed virgin mother looks upon her only child with wonder and mystery, amazed that she should have been chosen by God for such an incomprehensible honor. Shepherds bring the message of the angels to Joseph and Mary, telling them the celestial announcement that their son was the Messiah. After some time, magicians from far away lands recognized the significance of the event and came bringing gold, frankincense, and myrrh.
But he came to what was his own, and his own people did not accept him (John 1.11). Although he could say, The whole earth is mine (Exod 19.5), yet the very persons for whom he came did not recognize him. And likewise for us, living in the 21st century: Christ comes to us in different forms and we don't recognize him.
How do we prepare ourselves for this moment? Everything, myself and yourself included, was created for this moment: the arrival of Christ on Earth. How will I present myself before him? Are my clothes sullied? Do I love him, or do I fear him? I have to offer myself regardless; let me at least be the sort of gift he would be glad to receive. Just as Gregory of Nazianzus said: Christ is born; glorify him. Christ is from heaven; go and meet him. Christ is on earth; be exalted. O All the earth, sing unto the Lord.
And Christ in turn is happy to receive us. He says: Here am I, and the children whom God has given me! (Heb 2.13). In his goodness and unsurpassed mercy, Christ receives all who believe in him, granting them the power to become children of God in spite of their prior sinfulness (John 1.12), and he will never turn away any who come to him (John 6.37). So in the light of all this: Christ is born; glorify him! Christ is from heaven; go and meet him!