Catechism of the Catholic Church §2745 — excerpt
Prayer and Christian life are inseparable, for they concern the same love and the same renunciation, proceeding from love; the same filial and loving conformity with the Father's plan of love; the same transforming union in the Holy Spirit who conforms us more and more…
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: Origen, De orat. 12: PG 11, 452c