1-when you lose?
2- when you win?
Both but with limits. I usually completely stop for a while whenever I lose/win an amount which I considered as my limit. I usually set a limit on my profit/loss to control my gambling because I will surely be addicted without any parameters on my games.
Remember that profit on gambling is limitless that’s why many people keep betting even though they already win enough since they can still play and potentially win more but no one take in consideration the house edge of the casino slowly killing players the longer they play.
It’s important to always have a limits on gambling or else you will never get out of the cycle of winning/losing until your got broke.
The best way to draw a line and put it into practice is when you set a time limit for your gambling activities and have a gambling budget so that you don't spend unnecessary on gamble. If you have exhausted your budget for that day, you quit the game and if it happens that you are in profit, your time limit will make you stop when it elapse.
It is good for a gambler to always know when to wmquit the game whether winning or losing so that you don't end up putting yourself in the risk of losing more to gamble.