Before people can have a steadfast faith for the healing of their body, they must be rid of all uncertainty concerning God's will in the matter. Appropriating faith cannot go beyond one's knowledge of the revealed will of God. Before attempting to exercise faith for healing, one needs to know what the Scriptures plainly teach, that it is just as much God's will to heal the body as it is to heal the soul.
When your eyes are upon your symptoms and your mind is occupied with them more than with God's Word, you have in the ground the wrong kind of seed for the harvest that you desire. You have in the ground seeds of doubt. You are trying to raise one kind of crop from another kind of seed. It is impossible to sow tares and reap wheat. Your symptoms may point you to death, but God's Word points you to life.