Sister Lucia, one of the three visionaries of the Virgin Mary at Fatima in Portugal, repeatedly said that prayers and sacrifices offered for the conversion of sinners form the core of the devotion to the Immaculate Heart of Mary.
Father Thomas McGlynn, an American Dominican priest who wanted to carve a statue of Our Lady of Fatima, asked Sister Lucia what Our Lady’s main message was. She replied: "The conversion of sinners and the return of souls to God. This plea was reiterated in all her apparitions. That is why I consider it to be the essence of the message." (Strictly speaking, the Blessed Virgin addressed this theme in only three apparitions, the first, the third and the fourth. But it was also mentioned in the three apparitions of the Angel in 1916, so in total, in six of the nine total apparitions.)
Similarly, on August 12, 1946, one of the founders of the Blue Army, John Haffert, asked Sister Lucia the same question: "What is Our Lady’s main request?" "Sacrifice," replied Sister Lucia. "And, sister, what do you mean by sacrifice?" "By sacrifice, Our Lady said that she meant the loyal fulfillment of each one's daily duties." "But surely the Rosary is important?" "Yes it is, because we must pray in order to obtain the strength to be able to carry out our daily duties."
Adapted from Fatima 100