From St. Bridget as quoted in Fr. Paul O'Sullivan's The Wonders of the Mass:
One day when I was assisting at the Holy Sacrifice, I saw an immense number of Holy Angels descend and gather around the altar, contemplating the priest. They sang heavenly canticles that ravished my heart; Heaven itself seemed to be contemplating the great Sacrifice. And yet we poor, blind and miserable creatures assist at the Mass with so little love, relish and respect! Oh, if God would open our eyes, what wonders should we not see!