Christ— who is God, who is the Almighty Word— created in the soul of His mother the feelings she was to have about those whom He, by being born of her and living His mysteries in her, wished to constitute as His brethren. The Virgin, for her part, enlightened by the grace that abounded in her, responded to this appeal of Jesus by a Fiat, a “Let it be done to me,” in which the whole of her soul poured itself out with submission and in oneness of mind with her Divine Son. By giving her consent to the Divine proposing of the Incarnation, she agreed to enter into the plan of the Redemption in a unique capacity; she agreed not only to be the mother of Jesus but to associate herself with the whole of His mission as Redeemer. To each one of the mysteries of Jesus she was to renew this Fiat that was so full of love, right up to the moment when, after having offered on Calvary for the salvation of the world this Jesus, this Son, this body she had formed, this blood that had been her own, she was able to say, “All is consummated.” At that blessed hour, Mary had entered so far into the feelings of Jesus that she can be called “Co-redemptrix.” Like Jesus, she at that time, by an act of love, completed the bringing of us forth to the life of grace.
—Blessed Columba Marmion, Christ, the Life of the Soul
Saint Louis Catholic 