The Gospel— unadulterated— is the flat announcement of MEGA (μέγας) joy for all people (Luke 2:10).
The heavenly song— the unveiling of the Incarnation in the birth of Christ— is the declaration that fear is finished business; that minds long darkened and impoverished by despair are no longer condemned to live among their own shadows. God Himself has done the unfathomable He has entered our condition in a body like our own, assuming our humanity in full, so that humanity might assume His Divine Life. In this taking-up, the Imago Dei (the Divine Image) is rediscovered— not as abstraction, but as the Divine Smile returning to human faces.
It is therefore no exaggeration, as Martin Luther so bluntly put it, to say that the whole affair can be nothing other than laughter and joy.