If a man deceives me one, shame on him. If twice , shame on me.
Explanation
somebody who is taken in by a hoax or swindle on one occasion may justifiably blame the perpetrator , but those who fall victim a second time have only themselves to blame.
Proverb
If a pig had wings, it might fly.
Explanation
some things are not just improbable, but downright impossible: said to some body who puts forward such a suggestion.