You are correct their is no perfect strategy that guarantee winning, no matter how good the person is with predicting game it does not guarantee 100% success so their is no point in borrowing money to gamble in such condition because at the end of the day the person will lose the money to gambling which is what the over confidence will cause, borrowing to gamble is not worth it.
Gamblers only borrow money when they want to continue but they are out of balance. There is no guarantee that upon borrowing, they'd win.
You guys are right about it and that's why even if they borrow a thousand times, there is no guarantee they'd win but they will increase their chance of winning because they have money to gamble again.
But the matter here, they're about to lose money once again and could enter into a cycle.