Obviously it is because it goes into his head, thinking that he might always get lucky if he'll push his luck to its limit, which clearly explained that it can't. Gamblers who don't know how to control their emotions and urges to have more profits will eventually lose their profits in the end of the day, the worst part is that they will never make profits again, I mean it will take some time before they would experience the joy when they are winning huge profits.

They key is to be contented no matter how big your profit is, it is safer that way, nonetheless, proceed with caution and take the responsibility to yourself.