How many times have you said that to yourself? usually we only say this when we've already lost badly.
From my experience on looking the actions of many people, I believe that this is the moment when people start gambling, not the moment when they say that they'll stop. When people lose money, they want to stop gambling but they want more to gain back what they lost and they want to stop gambling after that but the problem is that when they continue gambling with this purpose, they lose more and it's getting harder to gain back everything they lost. Day after day, it becomes a habit and then it becomes an addiction. The only way to stop it is to say goodbye to old loses and to never think about them.
Days or weeks pass, emotions settle down, we get our hands on some extra cash, and suddenly we're gambling again.
Have you ever been in that situation yourself? How many times have you promised yourself you'd stop gambling only to find you're still doing it today?
I've never been in such situation because I gamble for fun, not for profit. That's the way to go.