Insanity is doing the same thing over and over and expecting a different result so I'm trying to be different in my approach to this.
Here's another way of saying it: fool me once, shame on you. Fool me twice, shame on me.
The goal is to win the victim back, at any price.
Alcoholics cling to co-dependents because they can't assume the responsibility of caring for themselves. By staying you're offering tacit approval for his behavior.