You can lead a horse to water but you can’t make it drink.
Your guess is as good as mine
You can’t fit a round peg in a square hole.
You can’t take it with you
You can’t always get what you want.
You can catch more flies with honey than with vinegar.
Your Guess Is as Good as Mine
You show me the man and I’ll show you the rule.
You can’t have your cake and eat it too.
You can’t teach an old dog new tricks.