Cease saying, “I prayed for many things and was not heard.” For even this occurs often to your advantage. Since He realizes that you lose heart and are indolent, and that when you attain your need you depart and no longer pray, God protects you with the pretext of need so that you may converse with Him more closely and devote yourself to prayer. For if you are lazy when you find yourself in such necessity and want, and do not persist in your prayer, what will you do if you lack even one of these things?? Therefore, God does this for your benefit, wanting you not to abandon prayer. Thus, keep praying and never be lazy, because prayer can accomplish many things, my beloved. Never approach prayer thinking that it is a trivial matter.
~St John chrysostom on Repentance And Almsgiving Homily 3
Fathers in Iconography 