Thus Christian chastity, as well as Christian humility, is grounded in the mystery of grace. In this mystery both virtues have their foundation and their law; from it they draw their vitality, and their relation to this mystery is similar to their relation to the Divine maternity in the case of the Blessed Virgin Mary.
Humility and virginal chastity were the principal and most peculiar virtues of the Mother of God. These virtues were a necessary preparation for her sublime maternity, as they were in turn nourished and fostered by this maternity.
The Blessed Virgin, now, is the arch-type of the children of God; as these resemble her in her supernatural dignity, so must they resemble her in those supernatural virtues ; and as Mary was incited to the practice of these virtues by her exalted vocation, so ought we to be animated to the same practice by the recollection of our high vocation.
As these virtues were never perfectly practiced on earth before the Mother of God, so they flourished after her, only where, by faith in Christ, the mystery of grace was known and glorified. Where grace is neglected or ignored, then these virtues will decline and be lost. Only where grace is appreciated in all its glory, will these virtues be understood, valued, and fervently practiced.
Taken from The Glories of Divine Grace by Fr. Matthias J. Scheeben