He is not chasing losses because he wins more than what he has as capital what happens here is that OP's Friend becomes Greed to chase for more wins and not leaning back about the losing he got.
He lose a bit but he got a big regret for this lose, when you are up and you are still thinking to win more, there's a chance that you'll end up with nothing because you will lose everything, that's pretty normal in gambling, one can start with a small bankroll get aggressive while gambling to win big amount and if it happen it happen, the problem is when to stop and just cash out to enjoy it.
If we can only get contented, we can always enjoy our winning by spending it to whatever we like to buy, then start a small bankroll again and try to win big just like what we have done previously, I think this is quite better than losing your winning instantly.