You must understand the type of game you are involve and you always need to have that hard stop to make sure that you are in the right track when dealing with your decision making.
Well, personally, I also say that things are very different when you're playing. There are always many things on our minds while we're playing, especially winning. But when we're winning, we believe that we deserve to keep winning, and that's the big mistake. That's where we have to stop.
It may be that when we're winning , it's only a small amount of money, but if it's enough to withdraw, then we have to do it. There's no other way, because it's better to withdraw it than to lose it, and understanding that is very difficult.
Quitting a game is indeed very hard for most gamblers as they tried to aim for more winnings, and usually end up screwing all their bankroll. Hence, it is always best to stick to your budget and call it a day if you believe you are already on your limits.