Basically we've tackled this in our circle of friends. Mostly, they are gamblers, but their answer is quite simple. as long as you haven't lose amount of your total amount of fund you've bet, you could try to play again and again. Once it exceed your investment or total bet, it is pretty fair to stop it right there, and go back when you have another set of funds to risk and play again. But in my opinion, I need to have almost 5 times of profit first from playing because IMO, it is not worthy to stop if you haven't earned allot.
with these words I am sure that you will not stop because you will never be satisfied in gambling. but if your goals are multiple profits then I think there will be time for you to get bored of gambling, especially if you can already get a lot of money from other methods which are certainly easier.