As much as we want to deny it, this is the reality. If ever you have someone that is close to you who has gambling problems, you shouldn't let them borrow money from you or to your other friends just to sustain his gambling habits. Even if they beg you, do not falter because giving in to such request could only just ruin his life even more. Because as we all know, gambling addiction is one of the major problems player fight with. If he already have an issue to begin with, then you shouldn't fuel his thirst to it.
Lending money is risky as well. As a lender, you don't have the assurance of when will the money you lent be paid back to you. Unless of course, you will make legal documents. But some of those who have contracts pay past due too and some even break their contracts, getting away with their debt. So yes, if you let your friend borrow you money, you can either lose money or lose both friend and money. In this part, you have to be firm. You have to stand your ground if money is important to you as well as your friend's well-being.
No matter how you look at it, it turns out that in any situation, lending money to a friend who will spend it on gambling is an erroneous and harmful decision. In general, there are different views on such things - some believe that a friend should be helped in any case, and some cynics believe that a friend should be left in trouble, because if this is not done, he will drag you there too ) There is sense in both points of view, but in those cases when help is needed even with the patient's resistance, only relatives have any real opportunities. From the point of view of the law, friends are just strangers.