If it's just a notification coming to you in the form of an on-screen message and pop-up, it can easily be closed and ignored. A more effective way of limiting your betting is if the limit actually prevents your from gambling. If you activate an 1-hour daily gaming limit and the time is up, the feature would prevent you from playing altogether. You would have to come back tomorrow to begin a new session.
Yep, I also think that one of the effective ways to cool down a keen gambler would be to prohibit the use of the gambling platform completely. For example, an option that, after some specific time or after a certain amount of money is lost, forcibly unlogged the gambler's account and doesn't allow re-authorization until a certain amount of time has passed.
That's like being cut off at a bar. But that might be effective on one casino, but a real addicted gambler has many accounts on many casinos, and he will just move to the next one.
In truth, there's nothing you can do except lock him up (physically)