" People can do great things. However, there are somethings they just can't do. I, for instance, have not been able to transform myself into a Popsicle, despite years of effort. I could, however, make myself insane, if I wished. (Though if I achieved the second, I might be able to make myself think I'd achieved the first....)
Anyway, if there's a lesson to be learned, it's this: great success often depends on being able to distinguish between the impossible and the improbable. Or, in easier terms, distinguishing between Popsicles and insanity.
Any questions? "

― Brandon Sanderson , Alcatraz Versus the Evil Librarians (Alcatraz, #1)