The shepherds were probably minding their own business that night, talking companionably with each other - maybe discussing the weather or their flocks, or their families, or complaining about the government. Even if their lives weren't wonderful, they probably didn't expect anything unusual. So we can't blame them if they were terrified by the sudden display of heavenly splendor. It was natural, then, that the first words from the angelic messenger should be: "Don't be afraid."
When the shepherds heard the rest of the message, they must have been filled with wonder. The angel announced a gift - a gift fit for royalty - a gift of light and joy and hope that was worth far more than a king's treasure. But that gift was not offered first to the rich and powerful people, and it did not come in a gold-encrusted cedar chest. This was a treasure that would be accessible to the shepherds, and to all people of humility: a tiny baby, wrapped in plain cloths, with a manger for a craddle.
Just as the Christ child presented the glory of God in a plain wrapper, Jesus continues to be present today in unexpected ways. He presents himself in the lives of people who are humble and gentle; those whose lives demonstrate God's love and forgiveness. If we look for glory in fame and wealth and earthly power, we may easily miss out on the treasure in a plain wrapper: "Glory to God in the highest, and on earth peace among those whom he favors."