Placebo

The Placebo Effect. Indubitably it works. But if one can mentally affect his body, thinking it was the placebo doing all the work, then most assuredly he can also mentally affect his body without the placebo. Of course, this would take tremendous work to master; for we are not born this day and age with complete control over our bodies. To become more Aware, to strengthen one's Will: these are good things. And they also have the side-effect of no longer needing placebos. Because if one is aware of his body, and exercises his will over it, then no outside agency is anymore necessary.

(Relevance: I was a bit tired a while ago - but then I got myself a sandwich, some coffee, and a bit of ice cream afterward, and poof! No tire anymore! Coffee usually doesn't have much effect on me, and I already had a bit of food not long prior. Yet these worked as placebos to give me energy. If my will were strong enough, I wouldn't need anything but my soul to give me energy!)