Catechism of the Catholic Church §2099 — excerpt
It is right to offer sacrifice to God as a sign of adoration and gratitude, supplication and communion: "Every action done so as to cling to God in communion of holiness, and thus achieve blessedness, is a true sacrifice."
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: St. Augustine, De civ Dei 10, 6 PL 41, 283