Yes, it's true that emotions will affect our gambling game if we can't control them, that's why I always say to beginners never gamble if you can't control your emotions, losing is something normal in the game, not something you should regret, let alone chase. losing is just to try to recover from losing, obviously that is the wrong way to be a responsible gambler, the most important thing for gambling is to control emotions and also controlling ourselves is very important because it can make us more focused in gambling.
Well, controlling emotions comes with experience. If you say that everyone should be perfecting and have control over their emotions, then I am afraid that is not possible.
When you gamble, you tend to flow with emotions, the winnings in gambling can make you excited and you can over gamble. Similarly, in case of a loss, you may feel depressed and anxious and due to this, you may gamble extra when you do not need to, (sort of revenge gambling). At the beginning, it will be hard for any gambler to control himself but as he gets experiences and faces losses, he will become a better and mature gambler.
Those who after getting experience in gambling, still not be able to have control over them, then such people are usually get addicted to gambling and they are not in a position to correct themselves or become responsible gamblers.