Simple for me, I'll say that I've won the casino or I've beaten the casino when I made profit (overall) not only in a single gambling session.
Others may say they have beaten the casino when they can stop gambling in the casino once they made a profit and not coming back at all.
However, as long as we keep on playing on the casino while we are still making profit, it is actually we cant beat ourselves (our greed).
I believe that is the truth, or a fact. Unless we stop, we are not yet winners. If we keep on coming back for more, there's always a chance that we might lose whatever amount we won. Worse, we might end up getting more greedy and bet all the profits that we made just to rush the winning amount.
I think those who quit are the real winners after they have made a profit. The urge not to come back is a winning moment against the casino, and as long as we can keep that, we are still winners all the way.