Last Sunday I gave an intro (from Wikipedia) into the life of St. Margaret Mary Alacoque. Here is what happened next:
One night she returned home, dressed in her finery, from a ball for Carnival. She experienced a vision of Christ, scourged and bloody, in which he reproached her for her forgetfulness of him, and of how His heart was filled with love for her due to her promise. As a result she determined to fulfill her vow and entered, when almost 24 years of age, the Visitation Convent at Paray-le-Monial on 25 May 1671, intending to become a nun. Alacoque was subjected to many trials to prove the genuineness of her vocation. She was admitted to wearing the religious habit on 25 August 1671 and she was admitted to profession on 6 November 1672.
In this monastery Alacoque received several private revelations of the Sacred Heart, the first on 27 December 1673, and the final one 18 months later. The visions revealed to her the form of the devotion, the chief features being reception of Holy Communion on the first Friday of each month, Eucharistic adoration during a "Holy hour" on Thursdays, and the celebration of the Feast of the Sacred Heart. She stated that in her vision she was instructed to spend an hour every Thursday night to meditate on Jesus' Agony in the Garden of Gethsemane.
On December 27, 1673, the feast of St. John, Margaret Mary reported that Jesus permitted her to rest her head upon his heart and then disclosed to her the wonders of his love, telling her that he desired to make them known to all mankind and to diffuse the treasures of his goodness, and that he had chosen her for this work.