But which gambler will simply stop? That is a very rare occasion and who gets to decide what is greed and what is the desire for relaxation and pleasure? It is like someone who loves to play poker and got lucky once big time. Telling that person to stop or believing that the person will top by themselves is not realistic.
But I agree with you that in a perfect world if someone gets lucky one time and maybe makes a lot of money, the best would be to stop or to continue in such a moderate way that whatever the person won will never be at risk to be lost entirely.
Gamblers who can just stop gambling are gamblers who have good self-control. When someone wants to continue gambling when they have won, perhaps it is because their greed has started to increase and if they cannot control themselves, they will only follow their lust to continue gambling. When that happens, a person will start to become addicted to gambling and if he continues to allow it, his gambling addiction will grow and he will not be able to control himself.
We can only limit our gambling activities so that we don't experience gambling addiction as a result of greed and taking bigger risks. We control gambling activities and not greed controls it, so we must really control ourselves in gambling.