Well, there is certainly some truth to the "Placebo effect", as it's known. In other words, if you think that you are going to get high, there's a 1/3 chance that you might actually get high.

A buddy of mine took that dried grass from under his lawn mower and sold it to a dude for about 50 bucks, saying that it was "good shit". He smoked it and actually got high. Gives whole new meaning to the power of suggestion. B: