Does God answer prayer or is there the possibility that God will say "No?"
Most people say that they have prayed and given up on Christianity because they did not receive an answer to their prayers, But when we truly understand the reality of what Jesus taught about prayer the one thing that becomes obvious is that all prayer is meant to bring an answer. Ask, and you shall receive. Seek and you shall find. Knock and it shall be opened. Everyone who asks, seeks, and knocks will receive, find, find an open door.
The only reason it does not work, to borrow a phrase from Chesterton, is that prayer "has not been tried and found wanting, but it has been found difficult and not tired."