Below are a couple of paragraphs by Max Lucado that rang true with me. It isn't the prayer that delivers you, it is the One to whom you pray.
We know that in everything God works for the good of those who love him. Romans 8:28
Prayer isn’t what heals us. God heals, not prayer. A matter of semantics? No. If you think the power is in the prayer and not the One who hears the prayer, you fault the pray-er for unanswered prayer. If I had prayed more, better, differently. It’s a depressing cycle.
Don’t assume that the faithful will never suffer.
Remember that Peter was in a storm before he walked on water. Lazarus was in a grave before he came out of it. In Matthew 26:39, Jesus himself prayed to be delivered from earthly pain. Please don’t interpret the presence of your disease as the absence of God’s love. I pray he heals you. And he will, ultimately.