Our very consecration to the Immaculate Heart of Mary calls upon us to make reparation for the offenses that we and others have committed against her. The Church, in inviting us to consecrate ourselves to her Immaculate Heart, implicitly calls upon us for this reparation. But more explicitly, and even before Fatima, Saint Pius X offered a plenary indulgence to all who on the first Saturday of the month would observe special devotions in honour of the Immaculate Virgin in a spirit of reparation for the blasphemies uttered against her.
There is, however, an even more basic reason why each one of us owes reparation to the Immaculate Heart of Mary: every sin of ours caused grief and suffering to her in union with her divine Son. For sin was the cause of that terrible day on Calvary when she, as the New Eve, shared in the torment of the great sacrifice, and, amidst indescribable pain, brought forth spiritually all the members of the Mystical Body of her divine Son. God willed that Mary should be intimately associated with His Son in bearing the burden of all sin; surely then, her Immaculate Heart, in union with His divine Heart, should receive reparation from us who have caused them such pain. If anyone causes hurt to even a very ordinary human being, he does not overlook the need to make amends. How much more do we owe to the Hearts of Jesus and Mary!
Excerpted Mary In Our Life, Fr. William G. Most