Borrowing money to gamble is the biggest and most dangerous mistake according to me because you would always be under pressure to gave back money and till that time you would have a lot of stress and would do anything to get money which could even involve wrong doings.
Indeed, borrowing money is a big No if you're going to gamble. It would be better to use your own money rather than asking for others to sustain your eagerness to gamble, its risky and might put you in a worse situation like what happened to op.
No matter how good player and confident you're to grow the money still its a mistake to use it for gambling.
Gambling can be full of temptation when you are actually in the casino. Jackpot price can be fulfilling if we won it and sometimes it makes a reason why some gambler attempts to borrow money for this. Not a kind of stupid thinking but it sometimes makes sense also cause what if he/she wins the jackpot prize, instant millionaire might he/she will be. But for us who are less experienced in gambling, we've never want to try this act cause we were afraid of the losses we might get.