You are very correct, greediness is not an emotion that should be found in a gambler, as the result of it is not always good, and does not benefit the gambler at all, there are other parts where greediness does benefit the bearer, like in the area of investment, it is commonly said that, "we should get greedy when other investors are fearful, and become fearful when other investors get greedy", this is some thing I've practiced one or two times and it helped me earn a nice profit...
But then, when it comes to gambling, we should completely do away with greed, as it will bring no benefit to the gambler, other than losses and more losses, and maybe an addiction will follow, if the gambler is not yet addicted.
A gambler is a person who gambles regardless of whether money is involved in his gambling or not. Without money and greediness, the excitement dries down and the gambler won't be interested in his gambling habit anymore. Greediness is what drives the gambler to take a risk and without it, he will never be able to make a profit. What he needs is discipline in his gambling habit as it stops him to become a gambling addict. You cannot ignore your loss! You can only wait for another time to gain your loss. That also depends on the ability of a gambler who has a stable mindset and a goal to achieve.