There's an old saying in Tennessee - I know it's in Texas, probably in Tennessee - that says, fool me once, shame on - shame on you. Fool me - you can't get fooled again.

Fool me once, shame on… shame on you. Fool me, you can’t get fooled again.

Fool me once, shame on you. Fool me twice, shame on me. Fool me three times, shame on both of us.

Mind what you do; if you deceive me once I shall never believe you again.

Fool me once, shame on you. Fool me twice, shame on my dopamine neurons.

Theoretical physicist Richard Feynman famously said, “You should never, ever fool anybody, and you are the easiest person to fool.” The moment you tell somebody something dishonest, you’ve lied to yourself. Then you’ll start believing your own lie, which will disconnect you from reality and take you down the wrong road.

One is never so easily fooled as when one thinks one is fooling others.

Only a fool can't be fooled.

Only fools offend me, woman, and they but once.

Mrs LINDE: When you've sold yourself once for the sake of others, you don't do it second time.

It is prudent never to trust those who have deceived us, even if only once.

If you once forfeit the confidence of your fellow citizens, you can never regain their respect and esteem. It is true that you may fool all of the people some of the time; you can even fool some of the people all of the time; but you can't fool all of the people all of the time. -Speech at Clinton, Illinois, September 8, 1854.

You must not fool yourself — and you are the easiest person to fool.

You can fool everyone else, but you can't fool your own mind.