Being so savagely tricked that you can't believe what just happened. (i.e. A teacher telling you don't need to worry about an exam and then giving you the most difficult test you've ever taken)

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.