If you think anyone is sane you just don't know enough about them.

See what I mean? You gotta be crazy. Ain't no time to be sane.

The cab driver is staring at me in his mirror. I'm talking to myself.
"The second sign of madness," I explain.
"What's the first one?"
"Killing lots of people and eating their genitals."
He laughs and sneaks another look at me.

Your own brain ought to have the decency to be on your side!

Perfect sanity is a myth propagated by straitjacket salesmen.

One must be sane to think clearly, but one can think deeply and be quite insane.