It's a trap that leads them to poverty, without any good control of your emotions you'll see yourself pushing for more thinking that if luck permits you'll achieved your goals, not realizing that it's just fueling your eagerness to win that huge amount, but in reality you are just favoring the house owner by continuing your gambling sessions with them, even sometimes you already win decently you just keep aiming for more and lose back eventually.
This is nothing more than the fact. People mostly think the best thing that can happen to a gambler is when he wins and the worst thing is when he loses. But in fact, the best thing to happen to a gambler isn’t winning because just as you’ve rightly pointed out, regardless of how much you’ve won, without self control you’ll still end up losing back all your wins to the casino and leave with nothing, it has happened to many of us a couple of times. So self control is paramount when it comes to gambling. Gamblers must at all time know how to control their emotions when they are gambling because there’s every tendency of losing it and that means losing control of your rational thinking and we already know where that leads us.
They should know their boundaries and limitations as without following it, the very chance that they will just repeat itself and continue losing their money, the tendency is to keep pushing yourself finding your luck but due to uncontrolled habits, instead of quitting you'll going to push for more, those kind of situations are the factors that leads each gamblers to poverty as there's no more limits with their gambling participations.