Matthew 24:44 

Therefore you also must be ready, for the Son of Man is coming at an unexpected hour.

The emphasis in this passage is on being ready to participate in the fulfillment of history; the fullness of what the gospels call the kingdom of God.  The message is clear: the priorities of our lives must center around the will of God - justice, love, mercy, forgiveness, life, wholeness, reconciliation, joy.  If we are conscious of God's presence in the little "advents" of every day, we will already be in line with what is yet to come...

We live our lives on alert.  Until we are consciously aiming our lives toward the promises of God we are not ready to celebrate Christmas.