When we feel like God has let us down, what is really happening? The reality is that God hasn't done what we expected him to do. But God is wiser than we are, and he sees the whole picture while we see only a moment. He can see that what he does to us is for our own good, to shape us and strengthen us.
We have to trust him.
For the foolishness of God is wiser than man's wisdom, and the weakness of God is stronger than man's strength.
1 Corinthians 1:25
Ask God to show you his plans for you, and have faith that even when it looks like things are going horribly wrong and your prayers are going unanswered - he is up there very busy molding and shaping you into a vessel that will be used for his kingdom.