As they say, prevention is better than cure.
This is not for gambling. For gambling, usually what you are seeing is the winning. Taking of risk is what gambling is, if you are not a risk taker then maybe gambling is not for you and maybe that is the sense that prevention can be apt but as a gambling then you are only heading for the winning. Most gamblers don't see limitation to what they want to bet until they are finished with it and the result is out to their favour or not. There are no prevention if you are a gambler, it is only those who don't gamble will run away after losing.
What @Gozie51 said is true because when someone gambles, he can afford to risk losing, and actually, he already knows that his chances of winning might not be too great. But because he took that risk, he still gambled, and gamblers just want to bet so they don't see the rest. So they think what will happen next is something they can think about later after gambling. And if they don't dare to take the risk of losing, they should stop gambling and relax at home, enjoying the atmosphere. Thus, they don't have to think about the risks of gambling or other things.