"May the people who lived in the darkness of ignorance
    see the great light of clear knowledge.  The old state that sin brought
    about has come to an end now all is new.  The letter ("The model
    of the laws of Moses") withdraws, the spirit prevails, the shadows leave
    quickly, as the truth arrives..
    This is what we celebrate today the coming of God towards
    mankind, so that we may come closer to - speak better with - return to God, so
    that we may now clothe the new man, as we have aborted the previous man. 
    The fall of Adam into sin resulted in mankind  becoming mortal,
    with Jesus coming as man we shall live forever. With Christ we are now born,
    put to the cross, and buried only to rise once again.
    Therefore we should not celebrate with festivals, but in a
    manner that is worthy of God, not in a manner that is worthy of man. 
    We should not celebrate in a manner pursuant to our interests, but celebrate in a manner that belongs
    and is worthy of  God.  Celebrating in a manner
    that does not lead to illness but rather leads to healing.  In such we
    should celebrate in a manner that is beneficial to our spiritual life and
    our salvation, not in a manner which is beneficial to our present
    existence."
    -Taken from St. Gregory's - 38th speech.
     
    Directly Related:
    The
    Origins of Christmas · An article that
    explains the origins of Christmas, and gives information on Greek Christmas.