Christmas was just the beginning
The birth of Christ is definitely "good news of great joy...for all people" (Luke 2:10). Yet Jesus did not remain a baby. His birth was only the beginning. Jesus grew to be a man "in wisdom and in stature" (Luke 2:52). He lived a life of perfection in order to fulfill the law, died our death on the cross as a payment for our sin and was resurrected from the dead to cause, "us to be born again to a living hope" (1 Pet. 1:3).
Still it does not end there. He ascended to sit on the right hand of the Father so that the Holy Spirit may come to empower us to be His witnesses here on earth. Pastor Mark Batterson succinctly captures this initial work of Christmas, "at Bethlehem, He is GOD WITH US. At Calvary, He is GOD IS FOR US. At Pentecost, He is GOD IN US". Seen in this light, we realize the triune work of God in our great salvation!