When it comes to gambling, it is all about luck. When you're lucky even the worst prediction you make will bring you money. The bad part you'll endup losing everything even when you're 100% sure on your prediction but you don't have the luck. From my understanding whatever the care we take and have statistics we'll fail if we don't have the luck. For this reason some limits being set for the day/week/month as suggested by the OP seems to be the better choice.
Well, there's even nothing like 100% accuracy in prediction because you can only predict, but you are not in the game to decide who wins and who does not win. Having statistics is just making sure you have your target amount to gamble off and also the days you wish to be gambling so that you don't end up being addicted, incurring more losses, or even wagering more than the amount you intend to. There are some people who don't really have plans for how much they wish to gamble off in a day, so any time they hit the casino, even if they have like $500 in their pockets, they will just use all of it to gamble. While they never intended to gamble with all that money, they will just get carried away with the fun until they have lost everything before they realise themselves.
You are very correct, in the aspect of gambling with money that was never intended to be used for gambling, it sure happens and that have happened to me once, being someone who is not addicted to gambling, I immediately learnt from it and promised myself not to make same mistake again.
One thing I've discovered is that, when it comes to gambling, you need to keep money away from you, that is only make available to yourself only the amount you need or have budgeted for that gambling session, have anything more means you are likely going to spend everything, like for example, I could have $500, and my intention is to gamble with $50, then leave $450 at home and only go to the casino with $50, this strategy helps in the sense that, when the $50 is exhausted, you will have no option other than to get up and find your own way, but if you go to the casino with the entire $500 and plan to only gamble with $50, the chances that you might end up gambling with that entire money is very imminent.