From In the Beginning was the Command Line: That feeling you get when you realize that 'save' in a word document doesn't really save the version, but destroys the previous version and replaces it with what you can see at the moment.

A realization that a computer isn't really your desktop, you're not really creating folders, and the paperclip doesn't love you. Metaphor Shear is probably responsible for many of the issues that normal people have with computers.