Double shame

My office and I were discussing phrases and there is one that we can't think of. It's something like Shame on you Shame on me ... used when someone forgives someone else the first time, then the second time its their fault. Is this making any sense??? If anyone can help please do!

"Fool me once, shame on you. Fool me twice, shame on me." Once bitten, anyone with any smarts should indeed be twice shy.