As the questions says, when do you stop? your point of no return?
a. at least double your money, then stop
b. you only stop when you have lost all your bankroll money and then blame the casino?
c. or you are a superstitions gambler, when you have signs like losing 3 straight in a row, then you quit because you know that you're having a bad luck
d. you stop when you are at least break even
I didn't include chasing your losses as obviously you might to continue.
I believe I am rather within the third category, that would be quitting when I realize luck is not on my side during the session, that is something I have pay attention to when I play fast-paced casino games, like dices or mines. If I start to lose money five times in a row I simply log out the casino, that is also a type of defense mechanism against loss chasing. If I stayed, I would feel tempted to chase my losses and we all know how that ends up for the majority of people.
It is better just to realize one is having a bad day and stop on time, before taking choices one will end up regretting.