Catechism of the Catholic Church §2734 — excerpt
Filial trust is tested - it proves itself - in tribulation. The principal difficulty concerns the prayer of petition, for oneself or for others in intercession.
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.