He Should Daven Repeatedly

Rabi Chama b’Rabi Chanina said: If a person sees that his davening has gone unanswered, he should not despair but should rather daven again, as Dovid Hamelech taught (Tehillim 27:14), “Place your hope in Hashem” in prayer, and if your tefillah was not answered, then “strengthen and encourage your heart” – strengthen yourself and don’t stop davening, but rather continue to “place your hope in Hashem.”

(Berachos 32b)