it's easier said than down because emotions are one thing that takes years of practice to control this is the more reason why more people fall victim to gamble related addiction which helps them to become broke
I do not disagree with you and it is my mind saying thing that controlling emotion is too hard and almost impossible to a lot of people (majority people can't control emotion and it is not possible for them) and that is why people become loser and loser dayyy by day and if win then still they can't utilize the fund in a proper way and that can be in lost today or tomorrow.
Another thing that makes it too difficult is when gamblers fail to see and understand how gambling works. When money is lost in gambling and it is an amount that you can afford to lose, you may feel bad about it, but after some time, you will get over it. However, if it is something that you can't afford, you will definitely get emotional about it. Most of the time, the reason why some gamblers feel so emotional is the mindset they have regarding gambling, which makes them expect so much from it.
It contradicts the intention of having fun when you are in pressure trying to win, and most of the time gamblers seek for profits and only few are really playing just to kill some time, it's a self define capabilities when you are able to make a hard stop while playing, setting limitation is a decision that's needed to prevent losing a lot.
And like what you said, when the amount that you use is something that you can afford to let go, then your apetite with gambling solve it all but if the amount that you use is something that's not intend for gambling, it change the mood and may lead you losing everything.