The only way to quit gambling for good is to eject it from your everyday life, dont think you can control it, that is just an illusion, forget about it, stop gambling and begin to do other stuff to entertain you.
As far as an addicted gambler will go - that is totally impossible. This type of radical approach never gets one in control of their addiction. Its important to understand that gambling and other addictions feed on people's minds and they have to control it step by step and not once and for all. One needs to decrease the amount they gamble then decrease the time for which they gamble. Parallel to it they should work on other things that they have interest in.