Believing in something only to learn it is not what you thought. I.e. to fully believe a religion or government is benign and perfect, when actually it is either corrupt or has to do dirty things to get the overall job done. A quest to accomplish something for a cause when actually you must overturn the cause.
I have to admit, I get some ideas from Final Fantasy X for PS2 that I’m playing right now (Yuna against her religion, Yevon). But, hey, get ideas where you can.