Catechism of the Catholic Church §1723 — excerpt
The beatitude we are promised confronts us with decisive moral choices. It invites us to purify our hearts of bad instincts and to seek the love of God above all else.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: John Henry Cardinal Newman, "Saintliness the Standard of Christian Principle," in Discourses to Mixed Congregations (London: Longmans, Green · Co., 1906) V, 89-90