One difficult thing to erase is your perception about books, movies, & people you formed in the past, with your mental state & maturity at that point of time.

You have changed, your thought process has changed, but your perceptions remain the same.

A movie you thought was a masterpiece, a person you thought was a genius, a place you called home where honey & milk flowed, all of that is shattered when you revisit it with your updated world view. There should be a word for this disappointment.