The smile of the contemplative in the presence of the Beloved is merely a physical expression of the total joy one perceives as one communes with God. St. Bernard used to say, "The joy of being in love is in the very loving." In other words, joy is not to be sought for itself, but is a by-product of love, and the smile is but the physical, exterior expression of the inner joy-love.
~ from ANGELS by F. Thomas Francis