Helena Kowalska is born in Poland in 1905. Seven years later, she hears a call to dedicate her life to God. Later she announces her intentions to enter a convent; her parents "decidedly oppose this move" that would send their 17-year-old daughter away from them (Diary xxx).
In 1924, Helena Kowalska applies to join a convent in Warsaw. Told by the superior that she is "no one special" and that she should earn money for her wardrobe, she works for a year as a domestic helper and then goes back to try again. She is accepted in 1925 at the Congregation of the Sisters of Our Lady of Mercy. There she will wear a novice's habit and bear the name Sister Maria Faustina.
Over the next 13 years, Faustina experiences an enormous variety of spiritual doubts and ecstasies. She begins keeping a diary under the guidance of her spiritual director. Here she records her struggles to follow Jesus. In 1938, she dies of complications from tuberculosis.
She is beatified in 1993 and canonized in 2000.
Today St. Faustina is best known for her 1931 vision of The Divine Mercy, an image of love and mercy streaming from the Sacred Heart of Jesus. Below are the words Jezu ufam Tobie ("Jesus, I trust in You"). Faustina arranged for the image to be painted, and it now stands in many Catholic homes and churches around the world. There are several versions of this image; see here for more information on "Why So Many Images? Which One Is 'Best'?"
I read Sister Faustina's diary over a period of several months in 2014-2015. It is fascinating, not only because of her mysticism, but also because she recorded her revelations in language that is heartbreakingly beautiful. She also speaks frankly about the trials of living with other people and maintaining her inner spiritual life. From the outside, Faustina is a quiet, uneducated nun who had no particular impact on anyone during her lifetime. But the impact is more subtle. Reading her diary is an exercise in awe.
Source: Diary of Saint Maria Faustina Kowalska, Marian Press, 1987.