36 Let us not then be ashamed to confess the Crucified. Be the Cross our seal made with boldness by our fingers on our brow, and on everything; over the bread we eat, and the cups we drink; in our comings in, and goings out; before our sleep, when we lie down and when we rise up; when we are in the way, and when we are still. Great is that preservative; it is without price, for the sake of the poor; without toil, for the sick; since also its grace is from God. It is the Sign of the faithful, and the dread of devils: for He triumphed over them in it, having made a show of them openly; for when they see the Cross they are reminded of the Crucified; they are afraid of Him, who bruised the heads of the dragon. Despise not the Seal, because of the freeness of the gift; out for this the rather honour your Benefactor.
Source: Catechetical Lectures (New Advent)