Catechism of the Catholic Church §2648 — excerpt
Every joy and suffering, every event and need can become the matter for thanksgiving which, sharing in that of Christ, should fill one's whole life: "Give thanks in all circumstances" (1 Thess 5:18).
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.