What prevents a gambler from winning a lot?

What prevents a strong gambler who plays the game for at least 12 hours a day, from winning a lot? It is his unwillingness to stop. The adrenalin knocks out his brains completely. He rushes to win back having lost some money even if he is rather tired. Having won a thousand pounds he thinks is not enough and tries more. He wants to snatch a large sum forgetting how much money he has already lost in casinos all over the world. But previously they were drinks and shows which disturbed him. Now it is tiredness. If you try to see your favorite movies for 10-12 hours you will not be able to reason properly. He has to fight on several tables at a time and look up in the notes and make up decisions. The sums are often times as much as my some monthly salaries. Of course it is not hard for me to log a program in his computer which disconnects him in 8 hours. But this corruption will deprive of one of my friends.
So having experience of watching an addicted gambler for years I can give you some advice. If you start the game not for getting some adrenaline but to enjoy and win or loose a little first estimate your abilities. You should define your money and time limits for more productive work. Never exceed whatever you would see in the perspective. The game is not the prize but hard work. If you think differently – Viva Las Vegas!