The excitement of winning is really overwhelming and require lots of discipline to stop at that point before incurring lose weightier than the win.
But I think why some can't or won't stop is not all about the excitement but is about the greed of wanting more when it is even obvious that the next try is totally uncertain and blurry
It is hard to stop feeling excited when you are winning and you are getting real life benefits like money. If let's say a father started gambling and he is able to feed his family and buy their wants and needs because of his winnings, it is hard to control that excitement and he will surely continue it even more.
If you ask me when is the best time to stop, I will say it is when you are high on the joy or excitement and calm down before going again but not same day or even week
When you are high on adrenaline, it is hard to think properly and you might make decisions you will be regretting over time. So, calm down before you make another bet.