Speaking from experience, you must be careful when you are winning because it comes with a lot of temptation to continue playing. Gambling has a way of giving you money and taking x5 back from you, this might include the money you have worked hard to get. Losing your hard earned money isn't really pleasant and it might ruin you mentally if it happens continually. It's important to take breaks from it when you are winning Because if you keep pushing your luck you might end up losing everything you have won .
It is true that a gambler can become more addicted to gambling either because of winning or losing. There are some gamblers who become overconfident after a few wins that time can bring a big problem for that gambler. There are many gamblers who have lost many times more gambling money than they have due to small wins. And when a gambler loses money over and over again, he will definitely break down from mental point of view, making it difficult for him to win at gambling. So I will agree with you that if one can not over indulge in gambling but can satisfy oneself with small wins be it win or loss. Gamblers who regularly take breaks from gambling are definitely good gamblers.