the truth is that pride is the first thing you will have to battle before even talking about being envious of him. That you were the brain behind his joining gambling and maybe you've sweet talk him about how you've won in the past and how he can possibly win if he gives it a try and even went on to give him the initial money he used in starting the gambling is enough reason to feel a sense of unease in his consistent win while you continue losing. But then, you need to tell yourself the truth that you can't continue draining yourself out just because you want to prove a point or because you don't want to be looked at as a failure. Gambling has a lot to do with luck and when you've ran out of it, it's usually very deficult to gain it back using forceful means or by gambling more often than usual. The best thing to do is to tell him you want to take a break and then come back latter, if he's reasonable, he should read the correct meaning to that statement And  not force you into gambling irresponsibly.

Except you're being superstitious if not I don't see anything special about joining a fellow to a gambling hall and how it's going to affect the outcome of your gamble. Except for his advice courses you to change the choice of the games you choose in your gambling then you could avoid being in such a situation if not, that you're in the same gambling hall with an addicted gambler doesn't make you an addict, and this context, it's even going to help you more since he's regular in his wins and might just spark you up into your winning ways. Jealousy for me is an act of witchcraft and if you're not happy when a friend is winning you're certainly not a good person.