As a preparation for her mission Mary asked Saint Faustina to be faithful to the will of God, putting it ahead of all sacrifices and holocausts (Diary 1244). As her special and dearly beloved daughter, Mary asked that she practice the three virtues most dear to her and most pleasing to God.

Mary said to her "The very first virtue you need is humility, humility, and once again humility; the second virtue, is purity, the third virtue, is  love of God, my daughter , you must especially radiate these virtues" (Diary 1415).

With humility, purity, and love, Faustina would be equipped for her mission of mercy.

Mary as her special Mother instructed her also in the interior life: to love God, interiorly to carry out His will in all things, to commune with God with intimacy, to accept all from God, to keep her eyes on the cross, to adore the Holy Trinity, and to live only for God, and also Mary said, that when receiving Holy Communion it  was a special time for observing all of these.

Saint Faustina recorded in her diary "the more I imitate Mary, the more deeply I get to know God". For Saint Faustina, Mary was truly her mother and she often nestled close to her Immaculate Heart like a little child.

She was made by God a special daughter of the Mother of God, in order that she could be prepared by Mary for her very special mission:

Proclaiming God's Mercy, in preparation for the Lord's final coming.