This phrase 'To fall off the wagon' is usually said on a recovering alcoholic, which means that someone has returned to drinking alcohol after a passé of abstinence.
Example in use: "Anna hadn't had a beverage in a decade, but when her husband of eleven years left her, she fell off the wagon again."
Interesting fact about To Fall Off The Wagon
This phrase was first recorded in, Alice Caldwell Rice's Mrs. Wiggs of the Caggage Patch [1901], where the Mr. Dick says it to old Mrs. Wiggs.
