Probably a small number of people can boast of being able to walk away from a casino with a winnings, and there are many more stories of failure. Risking your last remaining money is not a smart thing to do. I don't think such people have any strategy or plan of action for sure. It's just a huge success that happens very rarely, maybe even once in a lifetime.
True, it doesn't usually happen. It is totally on luck. However, it is not unusual to win small amounts of money here. As happened to Smith. But he gambled with $5,000 for about a week and won $17,000. This amount is not very high in gambling where many people have records of winning millions of dollars with keeping very few dollars.