I would be frank with a friend. If my game was unsuccessful, I would pause and help my friend continue to win (or simply watch his success) by encouraging and warning against over-involved, which leads to losses..
I'll do the same thing too. I am not jealous if a friend is winning with his bet. I'll also support him and won't ask for anything in return. That's how we should do it because we don't see that very often and if they're on the opposite side and they're losing, we'd give them a warning for them to stop and contemplate their status whether to continue or not.
There is no point to hate someone who is winning in bets who's a friend to you or what if they're winning in life as well? are you going to hate them or not? we shouldn't.
If they have their winning time, if we clap to them then our time will come as well that they're going to clap with our victories.