The mainspring of the entire apostolic ministry of St. Louis de Montfort, his great secret for attracting souls and giving them to Jesus, was his devotion to Mary. On her he based all his action: in her all his assurance, and he could not find a more effective weapon in his time.
To the joyless austerity, to the dark terror, to the proud depression of Jansenism, he opposed the filial, trusting, ardent, expansive and effective love of the devout servant of Mary, refuge of sinners, the Mother of divine Grace, our life, our sweetness, and our hope. But also our advocate, placed between God and the sinner, who is busy invoking the clemency of the judge in order to bend his justice, and to touch the obstinate hearts of the guilty.
In his conviction and experience of Mary’s role, Father de Montfort declared with his characteristic simplicity that "no sinner had ever resisted him once he held him by the scruff of the neck with his rosary!”
But our devotion must be sincere and loyal. The author of the Treatise on true devotion to the Blessed Virgin distinguished it from a false, somewhat superstitious devotion, which follows external practices or superficial feelings but continues to live as it pleases and remains in sin, counting on a miraculous grace at the last hour. True devotion, that of tradition, that of the Church, that, we would say, of good Christian and Catholic sense, tends essentially towards union with Jesus, under the guidance of Mary.
Pope Pius XII (1876-1958)
Excerpt from his speech to the pilgrims gathered in Rome for the beatification of Saint Louis Marie Grignion de Montfort, July 24, 1947 (Translated from the French)