Controlling our emotions is making us able to control our money as well.
Because when our emotions have been mixed up, our control to our money is also losing. So if someone is good at one, it's possible to be good at both.
And then with having such qualities, makes a better and a responsible gambler.
You are correct that controlling emotions might help us to prevent our loss, but it is a matter of sorrow that almost every user, including me, loses control of emotions, and that's why we lose more and more money. So, controlling emotions is one of the most important factors to stop/prevent loss and also to make money from gambling.