The placebo effect works if your brain thinks that you think that it will work, if I understood things correctly.

And yes, that I can't reliably self delude, and even if I could it would be prone to backfire, is exactly what causes this to be a problem.

I'm decently sure that my brain does not store beliefs separately from confidence, affect, etc.

I thoguh that was exactly the point of the dementor sequence; that it was an impossible paradox.