The spirituality of Sister Faustina is very healthy, because, on the one hand, it guards against religionism (that is, against practicing the Christian life only in prayer), since it calls for performing deeds of mercy; and, on the other hand, it prevents practical horizontalism (which would reduce religiousness to performing charitable works), since her spirituality requires a living contact with God. In the school of Sister Faustina, we can thus acquire a solid knowledge of the most difficult subject; namely, the art of living in the spirit of childlike trust toward God and mercy toward neighbour. At the heart of this spirituality lies the knowledge and contemplation of the mystery of Divine Mercy in everyday life; its nourishment and strength is love of the Eucharist, its certitude – obedience to the Church, and its consolidation and model – devotion to Our Lady of Mercy.