~ That's right, as long you can control your emotions you don't need to stop, ever, even after winning a really big amount. For many people(and definitely for me in particular) gambling is not a way of making money. It can help to make money in other fields, providing you with relaxation, but it's not a money making tool in itself. If I found an ancient golden coin worth tens of thousands dollars while snorkeling, would I stop that activity? No. And the same goes for gambling.
It is not about controlling your emotions, it is about the feeling within whenever you win in gambling, the more money, the more happy you would be, and that is what drives us more crazy about gambling, that feeling would never make you tired, you will long for it everyday and that is when we take ourselves in addiction, it could be either or bad, it is good when you are winning everyday and bad when you lost everyday but still you keep coming back to play.
When it comes to number, humans would never be satisfied, because we like to accept things in our lives as long as we need---want it.
To prevent all those bad things you've mentioned, one has learn how to control his/her emotions. For example,
sadness is one of the basic emotions, and every gambler feels sad about losing a game. Now, those who are skillful in controlling their emotions can quickly switch to doing something else, and move on, while those who can't control their emotions will continue playing, either out of
anger(another basic emotion), or pursuing a reward to feel happy. And
happiness is also a basic emotion, and very dangerous one, by the way. People who are addicted to happiness are the most unhappy beings in the world.
So, in short, it is about controlling your emotions. So that you wouldn't have to ask yourself in despair, "How much do I need to win to stop gambling?"