Yes of course, basically everything that is done based on emotion will never be right, meaning usually the results will always be much worse because actions and decisions made based on emotion tend to be aggressive and far from your limits and that is the reason why the situation is usually much worse which in addition to losing more of your money will also increase the mental and psychological pressure of a gambler which is also what sometimes makes gamblers make crazy decisions like ending their lives or other decisions.
The point is, the ability to control oneself is indeed something very important that a gambler must have, as you said which does not only apply to gambling but also to various other things that happen in life.
Yes, you are absolutely right, I have seen many such cases. Unable to control emotions, people have lost their money by betting too much in gambling and finally they have broken down mentally. Those who gamble emotionally become so bad that they cannot come back from this state of excitement. I have seen many of us here who have destroyed the balance of their normal life by going on this gambling line.
It is really difficult to control our emotions, but emotions must be controlled all the time. If we cannot control emotions, it often becomes a bad aspect in our normal life. We should stay within the normal range, emotions should be controlled, then nothing bad will happen to us.