Catechism of the Catholic Church §2755 — excerpt
Two frequent temptations threaten prayer: lack of faith and acedia - a form of depression stemming from lax ascetical practice that leads to discouragement.
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.