By each Hail Mary we give Our Lady the same honor that God gave her when He sent the Archangel Gabriel to greet her for Him. How could anyone possibly think that Jesus and Mary, who often do good to those that curse them, could ever curse those that bless and honor them by the Hail Mary?
Both Saint Bernard and Saint Bonaventure say that the Queen of Heaven is certainly no less grateful and conscientious than gracious and well-mannered people of this world. Just as she excels in all other perfections, she surpasses us all in the virtue of gratitude; so she would never let us honor her with love and respect without repaying us one hundred fold. Saint Bonaventure says that Mary will greet us with grace if we greet her with the Hail Mary.
Who could possibly understand the graces and blessings which the greeting and tender regard of Our Lady effect in us? From the very first instant that Saint Elizabeth heard the greeting that the Mother of God gave her, she was filled with the Holy Spirit and the child in her womb leaped for joy. If we make ourselves worthy of the greeting and blessings of Our Lady we shall certainly be filled with graces and a flood of spiritual consolations will come down into our souls.
From page 47 and 48
Nihil Obstat, Gulielmus F. Hughes, S.T.L., Censor Librorium
Imprimatur, Thomas Edmundus Molloy, S.T.D., Archiepiscopus-Episcopus Brooklyniensis, 1954 For more, see The Holy Rosary
St. Louis-Marie Grignon de Montfort's The Secret of the Rosary