Salam
آب از سر گذشتن،
refers to someone that doesn't have anything to lose.
آب که از سر گذشت چه یک وجب چه ده وجب
means when you lose everything, nothing matters for you anymore!
We say: اون که آب از سرش گذشته
means: He lost everything, or, He lost his whole life and so on , depends on the status which we talk about.
Good luck