The theory is;
If you want to gamble, see it more like you are paying the casino or gambling platform to have some fun (just like you do to go watch some movies in cinema), which if you are paying for anything, you are not meant to expect it back. The good thing however is that, you can actually end up being paid more for having that fun if you get lucky, but the chances of seeing that happen is pretty slim. In that light, if you cannot actually live with doing what I said above, then you should not be gambling at all.
Does this sound like a mentality that can help anyone understand what they are in for if they indeed want to gamble or something even those who are tending towards addiction can set their mind to so as not to get into that deep gambling hole that is hard to come out from?
Then in my own conclusion, gambling is purely based on luck. Even if you are new or veteran in gambling if you are not lucky to win, you will eventually lose your resources if you get addicted to it. So see to it that when you gamble, make sure to gamble only the amount that is not needed for your daily expenses and savings.