Well, I've never been to a casino, but I did spent quite some time on videogames, including WoW. For me, the trick to actually give something like this up was to say to myself, "I can stop at any moment. In fact, I will stop right now" and... stop. The next few moments/hours/days (depending on how long you've spent and how emotionally attached you've grown) feel kinda surreal: "Have I really just spent all this time to... basically doing nothing", but it helps to switch your attention to something else and forget about that accident. I suspect, however, that this trick only works for someone pretty lazy i.e. someone who can easily refrain from doing something even when feeling like doing that something (imagine "Mood: Ich Hab' Keine Lust by Rammstein").