Personally I know many great gamblers, and they all have the same thing in common... Money managements skills. Normally being a gambler tends to come with being poor at managing your money. Most gamblers will end up losing a lot more than they think simply because they are not managing their money properly. So learn this first, keep track of every penny going in and out, and make sure you're never losing more than you can afford.
Experienced gamblers do not gamble every time, because they also know that regular gambling will not in their favor. When they realize that now it is time to quit, they dont wait in casino and leave the place. A good gambler always gamble only those games in which he has great experience and he can use gambling tactics and strategies as well to win the game.
Also, a good gambler will know his limit and will never break his own rule. Once he reaches the targets, win or lose, he will immediately leave the game. Good gambler has plan while the bad one will follow their emotions.
Of course, limit is one thing that has always been the thing that a lot of gamblers tend not to take into consideration most of the time and in that case, they flop so badly that they tend to make wrong decisions most of the time when it comes to their inability to put themselves in check and in control.
As long as you know how to not overstep your boundaries, place a limit for yourself and do things accordingly without having to overdo things or expecting something you cannot get, then you have been able to set a principle for yourself to guide you into not becoming an addict, which is the only thing that can make you a good gambler.