You know you've probably flipped when you suddenly sit up straight in your chair and declare: "I'm a moron!" The true evidence comes when you then spread your arms, in the posture of one displaying her moronity to the world and say: "Watch me be a moron!" Stand up, do a little turn, bow to the corners of the (empty) room and ask: "Don't I do it well?"

Of course, complete insanity would be evidenced by getting a response to that question.

(There is a reason I'm a moron, by the way. I'm not just doing this randomly.)