~snip~
In my personal view, talking about someone who is successful in gambling "is not about how much a person can win a bet" but rather talks "about how a person can control himself over the gambling activities he has been doing so far" which is where he is no longer influenced and provoked by the environment or by an offer that might make him do something stupid again when gambling.
Someone who is successful in gambling will never assume that gambling is a money-making machine that can give him profits. and someone who is successful in gambling will never prioritize his gambling activities compared to the responsibilities he is currently carrying out.
A succesful gambler is as rare as a unicorn.
To be one of those, you need to win big, which is rare, and do that before losing too much, which is also rare.
And on top of that you need to also stop gambling after winning, which very few people are prepared to do...
To make things short, there are no successful gamblers, only successful people, because if someone have made a huge win but continued on his gambling habits it will most likely going to drain every single penny he has. So, I don't think you will call that a successful gambler.
I will consider someone and to be called a successful gambler if he managed to quit gambling before things get worst mentally and financially. Successful gamblers are those who are done with gambling without getting his life ruined.