Incarnation is not yet resurrection. Flesh in Jesus, as in us, is human flesh, vulnerable, weak, and incomplete. Christmas celebrates Christ's birth into this reality, not his removal of it. The Lord redeems limit, evil, sin and sorrow. They are not abolished. There is a definite difference.
For this reason we can celebrate Christ's birth without in anyway denying or trivializing the darkness in our world and the very real struggle we can experience in our lives and within our Church. Christmas is a call to celebrate while still in struggle.
The incarnate God is called Emmanuel, God-is-with-us. That fact does not mean immediate festive joy. Reality has its harshness and Christmas does not ask us to make-believe.
The incarnation does not promise us heaven on earth. It promises heaven in heaven.
Here, on earth, it promises us something else – God's presence in our lives. This presence redeems because it is the grace of God-with-us that empowers us to keep on choosing the light, to not lose heart, and to walk on together in hope.