Not everyone sees life as a risk. There are cautious people who avoid risks by any means and I believe it is possible to do so if one truly wants to. If such people decide to play gambling games I think their approach would also be built around avoiding risks and this would be the safest way to engage in activities involving money risks. And for those who believe that risk is a natural part of life they will take risks in everything.
It's not just about risk, but about the person himself. Only he can control his emotions and actions. Teach him discipline and strictly follow its rules and guidelines. This should be a mandatory condition so that the player does not go beyond what is permitted. He could stop and leave the casino in time, from stopping gambling when it is really necessary to avoid negative consequences.