Most gamblers are seen chasing profits in gambling. You cannot handle it with emotions. Here people associate their emotions with their psychological standards. By learning to control emotions, you can prevent yourself from losing more in gambling.
The attitude of chasing losses is the reason why some new gamblers would think that gambling is a scam because they have lose a lot of money that they never have intentions of losing. Like you said, self control can help them become better gamblers but they still have the decision to make concerning how much they want to spend on gambling or not.