Well I think a true gambler is when you made up your mind to withstand any outcome that might comes out along the line, without having any thought. Because is already obvious that gambling involves losses and winnings, so is quite sating that each of them can actually happens at any given time. So as a true gambler you would always accept any outcome without panicking because gambling is more of losing than winning.
A true gambler is a person that gambles responsibly and knows the consequences of the actions they are getting their self into. This is out mostly important because people gamble for the sake of money they want to make and are not emotionally prepared for the outcome and when the going doesn't go as they expected, they lose interest and don't like the concept of gambling and some even blame the casino all the time for taking their money, some even call it unfair platform.
I think that the first job of every gambler is identifying how they can take full responsibility in gambling, some people don't know this but if your gambling finance can only afford to lose a dollar, don't go above that budget but money has a way it consumes a lot of people that are involved in gambling and when they lose so much, they don't even know how to control their games any more. It's the reason why many people becomes irresponsible gambler in the long run.