From Pope St. John Paul II’s encyclical Veritatis Splendor (1993):
Such is the consoling certainty of Christian faith, the source of its profound humanity and extraordinary simplicity. At times, in the discussions about new and complex moral problems, it can seem that Christian morality is in itself too demanding, difficult to understand and almost impossible to practise. This is untrue, since Christian morality consists, in the simplicity of the Gospel, in following Jesus Christ, in abandoning oneself to him, in letting oneself be transformed by his grace and renewed by his mercy, gifts which come to us in the living communion of his Church. Saint Augustine reminds us that “he who would live has a place to live, and has everything needed to live. Let him draw near, let him believe, let him become part of the body, that he may have life. Let him not shrink from the unity of the members”.182 By the light of the Holy Spirit, the living essence of Christian morality can be understood by everyone, even the least learned, but particularly those who are able to preserve an “undivided heart” (Ps 86:11). On the other hand, this evangelical simplicity does not exempt one from facing reality in its complexity; rather it can lead to a more genuine understanding of reality, inasmuch as following Christ will gradually bring out the distinctive character of authentic Christian morality, while providing the vital energy needed to carry it out. It is the task of the Church’s Magisterium to see that the dynamic process of following Christ develops in an organic manner, without the falsification or obscuring of its moral demands, with all their consequences. The one who loves Christ keeps his commandments (cf. Jn 14:15).
182 In Iohannis Evangelium Tractatus, 26, 13: Corpus Christianorum, Latin series 36, 266.
— Veritatis Splendor 119