Riyad-us-Saliheen 1744
Anas (May Allah be pleased with him) said: The Messenger of Allah (PBUH) said, "When one of you supplicates, let him be decisive and he should not say: 'O Allah, bestow upon me such and such if You wish', because no one has the power to compel Him."
[Al-Bukhari and Muslim]
One should pray to Allah will full confidence that He will answer his prayers. One should also persist in praying and never give in to despair.