It seems to me that while a lot of Christmas sentiment is normally centred upon the Incarnation, the God-Made-Flesh point, the gospel narratives by and large seem to focus upon the fulfilment of the hope of Israel, where after Israel had hoped, prayed, and awaited so long, God has finally answered and come. This was what made the occasion a truly joyous and happy one. I think Dostoevsky's The Brothers Karamazov actually captured the background feeling of Christmas very well in the chapter on the Grand Inquisitor:
Fifteen centuries have passed since He promised to come in His glory, fifteen centuries since His prophet wrote, ‘Behold, I come quickly’; ‘Of that day and that hour knoweth no man, neither the Son, but the Father,’ as He Himself predicted on earth. But humanity awaits him with the same faith and with the same love. Oh, with greater faith, for it is fifteen centuries since man has ceased to see signs from heaven.
No signs from heaven come to‐day
To add to what the heart doth say.
There was nothing left but faith in what the heart doth say... But those who remained faithful were all the more ardent in their faith. The tears of humanity rose up to Him as before, awaited His coming, loved Him, hoped for Him, yearned to suffer and die for Him as before. And so many ages mankind had prayed with faith and fervor, “O Lord our God, hasten Thy coming,” so many ages called upon Him, that in His infinite mercy He deigned to come down to His servants.
While this is a fictitious account of Jesus returning to visit his people in 16th century Spain, I think it does capture what the people of Israel felt in the 1st century.
For centuries since the Prophet Isaiah declared the coming of the Messiah, the hope of the salvation and restoration of Israel, the people of Israel waited, prayed, and hoped. Many had fallen away since, their hearts had since ceased to believe, their faith ravaged by the passage of time. Yet many others had continued to hold to the hope of the promise and the prophecy, with greater fervour they prayed as pagan kings and rulers conquered and oppressed Israel, as the memory of God's faithfulness to Israel and the mighty works He had done for her receded further and further in time, yet for the faithful those events were an ever present moment, and they maintained that hope in their hearts.
Yet as Proverbs 13:12 puts it:
Hope deferred maketh the heart sick:
but when the desire cometh, it is a tree of life.
For faithful Israel, the deferment of the hope of salvation made their hearts heavy, piety commands that they maintain that hope, but the deferment of the promised salvation sickened them with a great longing. But then suddenly, when the "desire of the nations" had come, "it is a tree of life", that is what turned their sickened hearts into joyous celebration, for at long last, the hope of Israel has come. Hope languishing against time had been given a new lease of life. God has been true to his oath.
That's why you can see throughout Luke 1 and 2 the continued emphasis on the fulfilment of the promise which God swore to Israel and their Father Abraham, that he would come and visit them and perform the oath which he swore, etc.
Thus, it seems to me, that the Christmas narratives in the gospels speak less about the mystery of the God-in-Flesh incarnation but more on the fulfilment of the hope of Israel. Many gods in many religions have taken flesh and have visited people unexpectedly, incarnated gods were not unusual throughout the world, what is particular about Christmas however is that it is the fulfilment of an eschatological moment, when all the covenants, oaths, prophecies, and promises issued before by God to Israel would be cashed in in the birth of Jesus, when God finally acts in time and in history to bring to fruition the plan of Salvation issued before.
We are living in the Dostoevskyian moment, after the First Coming and awaiting the Second Coming, 2000 years have passed since we were promised Christ's dominion over the world, and we wait still for that fulfilment. However, many of us, like Israel of old, had since ceased to believe, or our hearts had been so sickened by the deferred hope that it is close to death.
The hope we habour of God does not have to be anything as cosmic as the dominion of Christ over the world, it could be whether God will "visit" us in our own lives in our specific space and time. Maybe we had hoped something of God for ourselves but year after year, prayer after prayer, it has gone unanswered, and over time, the sickening of the heart approaches death. Yet, the Christmas narrative tells us, we will not wait in vain, some day in the future, that hope will be fulfilled, Jesus will come, and He did come long ago, and He will come again. As Proverbs says "but when the desire cometh, it is a tree of life". When, not if, He does "visit" us, we would rejoice as Simeon, Zacharias and Mary once did of old, when God finally visited Israel with the promised Messiah, his very own Son.
So let us remember the reason for the Season, it is the acceptable Season itself, that eschatological moment when God decided to make sacred that moment of history once for all: Anno Domini, and consummate all his promises, oaths, and covenants.
A very Happy Christmas to one and all.