YESTERDAY’S MAN OR YESTERDAY’S WOMAN
Someone, especially a politician or celebrity, whose career is over or on the decline is yesterday’s man or woman.
YOU CAN LEAD A HORSE TO WATER, BUT YOU CAN’T MAKE IT DRINK
This idiom means you can offer something to someone, like good advice, but you cannot make them take it.
YOU CAN SAY THAT AGAIN
If you want to agree strongly with what someone has said, you can say 'You can say that again’ as a way of doing so.