הלכה על ברכות 64:8

Every prayer has an influential effect, as Rabbi Ḥanina says, “The prayers of one who prays for a long time do not return unanswered” (Berakhot 32b). Sometimes the effect is immediate, and at other times in the distant future; sometimes the prayer is answered completely, other times partially. As the Sages say (Devarim Rabba 8:1), “Great is prayer before God. Rabbi Elazar says, ‘If you want to know the power of prayer – if it does not accomplish all it is meant to do, it at least achieves half.’” God is the One Who knows how to help and support a person. Sometimes, for various reasons, one’s misfortune is for her own good, and therefore God does not accept her prayer. Nevertheless, her prayer benefits her, and its blessing will be revealed in one way or another.