Why Peace and Good Will?

Why is it that at the birth of Jesus Christ the three wise men bring gifts from a distant land guided by a super-natural star and we see the shepherds glorifying Him surrounded by the radiance of the angles.  The angels teach them a heavenly song of praise - “ Glory to God in the highest, and on earth peace...” (Luke 2:14)  The angels told the shepherds, "I bring you good tidings of great joy, which shall be to all people" (Luke 2:10). So what is the reason and meaning of this joy and what is this peace that is spoken of? 

Now He who dwells on high and reigns over the celestial heights has the earth as His throne, and is glorified on earth as much as there by His saints and His angels alike.

Saint Gregory Palamas tell us the following,

Listen to the Gospel song to the end and you will understand. "Peace, it says, "good will toward men" (Luke 2:14)  For God, who was angry with the human race and subjected it to terrible curses, has come in the flesh, granting His peace and reconciling them to the heavenly Father. Behold, says the hymn, He has not been born for us angels, though now that we see Him on earth we extol Him as we do in heaven, but for you men, that is to say, for your sake and in accordance with your nature a savior is born, Christ the Lord, in the city of David.

Why is peace linked with good will?
Saint Gregory says,

Good will refers to that which is in and of itself well-pleasing, the original and perfect will of God. It was not the original and perfect will of God that He granted benefits, and not even perfect ones, to certain men or to on nation only. That is why, just as God called many people His sons, but there is only one in whom He was well pleased, so He gave His peace on many occasions, but only once accompanied by His good pleasure, which He grants, perfect and unchanging, through the incarnation of our Lord Jesus Christ to every race and to as many as desire it.

It is our responsibility to develop this same peace within ourselves though our participation in His Church.  This is the benefit He gave to us through the Incarnation.  It is is ours to "preserve within ourselves."