Realizing too late in my freshman year in college what a hick I actually was. It was something a little condescending and patronizing someone said about a stupid, tacky plaque hanging on my wall.  It wasn't that it turned me into a snob all at once at that moment - on the contrary, it made me really self-conscious. I think I realized how narrow my experience had been. Oddly, it made me more curious and more willing to expand my mind & broaden my taste. It helped me learn to be the guy - for better or worse - I've become.