What is the saying fool me once?

"Fool me once, shame on you; fool me twice, shame on me" is a well-known saying that warns against being deceived or taken advantage of repeatedly. It suggests that it is okay to forgive someone for fooling you once, but if the same person or situation fools you again, it is your own fault for not learning from the initial mistake. This saying encourages individuals to be cautious and learn from past experiences to avoid being duped again in the future.