What is the science behind 'miracle' recoveries, and can we implement it into mainstream medicine?

I'm referring to the x-factor, like almost an extreme placebo effect that undermines a doctor's zero chance prediction of survival, or recovery from a permanent ailment. It seems that in general, a positive outlook can sometimes produce such results, but (as far as I know) we don't really understand what is going on in the body/brain that causes it. Are we now, or will we ever be, capable of studying this anomaly, and if so, how could we implement it to advance mainstream fields of treatment?