This is a very hard question, but i think you must set you 2 limits.
1. The time limit. You set you a limit of 1 hour and you dont play not more than this 1 hour.
2. The winnings. You must set a winnings limit for example of 200 Dollar. After you won this 200 Dollar you dont play anymore this day.
Because without these 2 points it will be hard to stop imo.
I think time limit is a bad idea but setting a goal when you reach it, stop the gambling right away. The problem is second thought, which makes people think they can win more so just make a firm mind and withdraw all you have once goal is reached, dont think much.