If you are feeling greedy, the right thing to do is not to gamble at all. This kind of game is designed to make greedy people lose money. People who play for fun, on the other hand, have less chances of losing a lot of money, since they do not feel pressured to play over and over again.
I think if we want to control our greed on gambling we should swear first to do not achieve our limits in any kind of cases. We must sets some rules and follow it. I think there is not obligation to quit gambling at all, also because it's not easy. So greed can be avoided by using mind and heart, and think about the results.
Although it is great in theory it rarely works in practice. The reason for this is because when you gamble, and you win, and then you lose, it's like you are high on crack. Your reward system in the brain is all over the place and you can't really think rationally, this is why it's so damn simple to get stuck in a gambling addiction. That's why it rarely works giving yourself promises or swearing things prior to gambling.