Here is a brilliant article by Sam Storms on the relationship between faith and healing. The following is a small excerpt to wet your appetite:
we must recognize that the “belief” or “faith” here is not a case of a Christian forcing himself to believe what he does not really believe. It is not a wrenching of one’s brain, a coercing of one’s will, a contorting of one’s expectations to embrace as real and true something that one’s heartfelt conviction says otherwise. Jesus is not telling us that when doubts start to creep in you should put your hands over your ears, close your eyes, and say to those doubts, over and over again: “Lalalalala, I can’t hear you. Lalalalala I can’t hear you!” That’s not faith. That’s “make believe.” That’s spiritual pretending.