Positive mindset has nothing to do with gambling wins, the wins comes with hard work and luck, therefore such taught should not be considered, no gambler wishes to lose any of his game when he bets and a lot of gambler goes to gamble with the morning and set of winning yet still lose.
Don't be surprised that folk may have a positive mindset but still be experiencing more and more loss if they are not careful. Here is why, if today a gambler gambles today and loses that game, he may try to go back in, simply because he thinks that he may win the next time and after that comes another next time of loss...That is why I agree with what you said, folks should not even be concerning themselves with building a positive mindset, rather their focus should be on properly managing their risk, good bankroll management and the likes. And then can achieve this by ensuring that they have a limit and gamble within that limit. And also by ensuring that they only use the money that they can afford to lose, and when the loss comes they should just accept it and move on, without having to revenge that loss...