Here are many examples.
The main problem arises when the emotions overwhelm common sense. A trader becomes addicted to feelings, fears, greed, or other emotions, depending on the situations in which he falls. This provokes him to act recklessly, which in particular leads to a bad result.
Another negative factor is the impact on the health of the trader. If a person is under the influence of emotions 24 hours a day (and with emotional trading, emotions will be with you all the time!), then this causes a huge stress. I remember the days when I could not sleep at night, I woke up several times a night to check all the prices. In fact, in those days I practically didn't sleep. It is very negative on health, both physical and psychological.