What is Fell Off The Wagon?
1.
When one resumes an addictive/compulsive behavior that they are trying to control. Originally referred only to drinking, but is now used in reference to all sorts of things including drugs, smoking, overeating, eating cerain foods, masturbation, casual sex, pornography...
Joe hadn't had a drink in 10 years, but when his wife of 30 years left him, he fell off the wagon.