Every greedy gambler that don't want to let go of his losses will live to regret chasing his losses, because he will incur more losses. Self control is very important in any activity that can be habitual to us. Whoever lacks self control over his gambling activities can become addicted easily. We shouldn't gambe to put ourselves into a big problem that'll affect us mentally, instead we should gamble for fun with an amount that you can afford to lose.
It is reasonable to gamble for fun but how realistic is that. I always doubt that people gamble for fun since no one is happy when he losses money. Even for those who gamble for fun if there are such gamblers then the pleasure can only come when they win. Naturally, there is happiness which comes from winning and this happiness brings the fun. It is not normal for a gambler who claims to be gambling for fun yet when he losses he gets angry. The implication is that such a gambler will get angry most of the times since gambling is unpredictable and so gamblers tend to lose more than they win making it challenging to even gamble for fun.
I think that the only motivation to gamblers is not to gamble for fun but rather to make extra cash. There is certainly other activities a gambler can engage in and get utility for his money and the desired fun. I have seen people gamble recklessly in the name of gambling for fun and regret at last. I have also seen gamblers chase wealth and then lose the little they have. Thus, the saving grace for gamblers is not to gamble with greed as you mentioned every greedy gamble would regret if he cannot let go of his losses. So, regardless of whether a gambler gambles for fun or not, there is a need to gamble without any element of greed.