And that saying created lots of addicted gamblers,

though seriously speaking there are gamblers who can work with their temper and able to quit with a good amount of winnings, but most are ain't capable of doing so, they will continue to try exceeding from their luck thinking that they can still have more winning streak.
Like what I mentioned above, more on your characteristics and your good judgement to stop when you already win,
Quitting in the right timing makes your gambling an enjoying and productive session.
For a gambler who doesn't have any rules, stopping when he wins is very difficult, because the more he wins the more he wants to keep playing until in the end the victory becomes a defeat. They are gamblers who are addicted or addicted, no matter what happens they still gamble. People who are serious and have control over their gambling I rarely meet, it's really about the characteristics and how they judge gambling. Gambling and staying productive is everyone's dream, but psychology can't be controlled when it comes to gambling.