Pope Pius XII
“Our Savior is continually pouring out His gifts of counsel, fortitude, fear and piety, especially on the leading members of His Body, so that the whole Body may grow ever more and more in holiness and integrity of life. When the Sacraments of the Church are administered by external rite, it is He who produces their effect in souls. He nourishes the redeemed with His own flesh and blood and thus calms the turbulent passions of the soul; He gives increase of grace and prepares future glory for souls and bodies. All these treasures of His divine goodness He is said to bestow on the members of His Mystical Body, not merely because He, as the Eucharistic Victim on earth and the glorified Victim in heaven, through His wounds and His prayers pleads our cause before the Eternal Father, but because He selects, He determines, He distributes every single grace to every single person ‘according to the measure of the giving of Christ.'”
Source: Pope Pius XII, MYSTICI CORPORIS CHRISTI, 6/29/1943