故态复萌
Return to one' s old habit.
Back in the old rut.
At one's little games again.
Return to one' vomit.
He that has done ill once will do it again.
Fall from grace.

eg：The thief was out from the jail but returned to his old habit to steal in the market.

中英俚语俗语来源：后汉书："帝曰，狂奴故态也。"

同义词：贼性难改 Once a knave and ever a knave.
反义词：改过自新 Turn over a new leaf.