You cant convince a gambler to stop gambling until he loose all. Never gonna happen, their addiction on a level of a crack heads.

The only way they stop is if they make such decisions.

I know one guy he stopped gambling, he was doing this for many years and never wanted to quit. What made him. Well, one day for 2 years in a row he start loosing non-stop. And he never had money. After that he made decision to stop gambling for good. How long this will last no idea, but he doesn't gamble for 6 month so far.