If this is successful, the gambler should be able to stop gambling rather than continue gambling because it will not always be successful in winning. They will not always be able to win and must be able to control their greed so that it does not create difficulties for them. By always controlling themselves when playing gambling, they will realize that winning is not easy and they have to have many things before they can win. Skill and luck are required to win so if they have already won, it is time to stop gambling and leave the casino.
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.