You can say that again
You can’t fit a round peg in a square hole.
You can’t unscramble a scrambled egg.
Your name is mud
You can catch more flies with honey than with vinegar.
You can’t make an omelet without breaking eggs.
You can’t have your cake and eat it too.
You can’t take it with you
You can’t teach an old dog new tricks.
You show me the man and I’ll show you the rule.