You can’t always get what you want.
You can’t take it with you
You can’t teach an old dog new tricks.
You can lead a horse to water but you can’t make it drink.
You can’t have your cake and eat it too.
Your guess is as good as mine
You can catch more flies with honey than with vinegar.
You can’t make an omelet without breaking eggs.
Your Guess Is as Good as Mine
You can’t unscramble a scrambled egg.