Mental negative patterns create diseases in the body: this is Louise Hay's credo and she explains what good affirmations are to be used in order to change our way of thinking and release old thoughts which contributed to block our good energy in our body.
Some years ago I would have thought: "Well, this is stupid", but the events in my life make me now believe that dis-ease can also have mental and even spiritual origins.
While I do not agree with Louise Hay's Law of Attraction, because it seems to me a wrong means and not very spiritual, I accept instead the idea that if we let forgiveness and love permeate our life, we see positive changes in our health and life.