You know you will have to stop when you have nothing to bet, nothing to get back and broke.
Its hard to stop specially when youre in a moment of cloudnine the Bam! Youre busted!
Well, I stopped when I had lost, and my money ran out. however, I limit the use of bitcoin I used to gamble, so it did not make me lose a large scale. other than that I will stop playing when my profit has reached 50% of my initial capital.