13 In this regard, it is to be noted that both piety and love, though always renewing the same words, do not always repeat the same thing but always express something new issuing from the intimate sentiment of devotion. And besides, this mode of prayer has the perfume of evangelic simplicity and requires humility of spirit; and, if we disdain humility, as the Divine Redeemer teaches, it will be impossible for us to enter the heavenly kingdom: "Amen, I say to you, unless you become as little children you shall not enter the kingdom of heaven" ( Matt . xviii, 3).
Source: Ingravescentibus Malis (Vatican.va)