I don't think he is saying it is all in your mind. What he is saying is that the mind has great influence over the body. Here, we are all "in the disease" so to speak. We focus on it, and give it energy, and what happens to things we give energy to? They grow. I think he is challenging us to try and "grow" health. To focus on health instead of illness, at least some of the time. That doesn't mean stop treating candida, but it might mean stop thinking about it 24/7. See if the mind can have some positive influence over the body. Think (and tell yourself) you are healthy, and maybe your body will repsond to that and start to become that. I have no idea how far that will take someone, but it is a concept worth thinking about.