Catechism of the Catholic Church §224 — excerpt
It means living in thanksgiving: if God is the only One, everything we are and have comes from him: "What have you that you did not receive?"
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.