I think this happens to addicted gamblers and most of us are addicted up to a certain point.However winning like 30 ETH is a big amount of money if started out with a small amount.If I won that amount I would stop immediately and cash out 20 ETH and then I would have continued to play until I win more or I lost everything.
It is essential for people to know difference the need and desire. Everyone wants to make lost of money from gambling but we also know some facts about it and should be reasonable enough to know that if we have some decent amount we should not become more greedy and quit and take money and only from the profits made if still want to continue can be done upto a certain %. But have seen people not only losing those profits but later on the money played with initial capital is also lost inspite of winning big amounts at some point of time.