sackcloth and ashes, to be in

To behave in a way that shows one's penitence or remorse for one's misdeeds or poor behavior. Darren has been in sackcloth and ashes ever since his girlfriend broke up with him for cheating on her. The former CEO is spending his days on a private island. He's hardly in sackcloth and ashes after defrauding customers out of millions of dollars, is he? Because there's no way to turn back time on the way I treated my brother growing up, I'll be in sackcloth and ashes for the rest of my life.

To be penitent or contrite; in a state of repentance. This term alludes to the ancient Hebrew custom of donning a coarse, dark cloth from which sacks were made and dusting oneself with ashes to signify one’s humility before God. It is mentioned in the Bible: “And I set my face unto the Lord God, to seek by prayer and supplications, with fasting, and sackcloth, and ashes” (Daniel 9:3). The term may be obsolescent.