I will will disagree with your topic OP. Maybe you should rephrase your topic again because you controlling your emotions cannot guarantee you success in gambling. If its is like that 99% of gamblers that knows how to control their emotions would be a successful gamber. Go and find out what controlling emotions means before bringing it to the public so that you wont change the narrative of what a successful gambler means or feels like.
Both of you are right actually and each gambler differs so basically we are seeing those gamblers that don't have control for themselves that they won't earn much money after they've just won in gambling.
But in real life, we don't know if they're the same person or there's already the life attachment for that daily gambler's life and then with the set of reality that he's dealing with and if he's emotional as well.
Anyway, it's true that someone's control over his emotion doesn't guarantee success in gambling but it helps right.
What matters is when they both control their emotions while they gamble, if they are not gambling for a better side which means they won't be able to control their emotions when they lose. And again staking randomly will also makes you to risk more than you can afford to lose, how because most atimes when your initial deposits are gone you will deposit another to bet those games which you haven't bet on. So there is no way one who's doing this will control him or her self when they lose, especially when they are not gambling for fun and not still gambling on a safer way.