A good gambler always focuses on his game and do not think anything else. It is good for winning a game because if you do not focus on your game, you will lose the game and your opponent will take all the money. Other thing is that you should fix a time limit for yourself and when the time ups, quit gambling immediately and also a limit for money putting in bet.
Well, focusing on a game as a good gambler is one thing and then knowing that everything is based on luck no matter how you focus as long as you are gambling is another thing and it is the latter that I believe actually makes you a good gambler as far as I am concerned. Like you said, it is always very important to limit yourself and set some restrictions. Everyone can be addicted if allowed, and that is one thing with addiction, it is no respecter of anyone, but it is only left for you to know this and know how to control those impulses whenever they start flaring up.
A good and experienced gambler look here and there in casino to find such persons that are not seems to be regular gambler because wining from such gamblers is easy. He always focuses on his game with full concentration, because if his mind is somewhere else other than gambling, he would not be able to win the game. He also fix limits for gambling and try not to accede that limit.