1/ Lack of Discipline— a) Not sticking to one strategy, b) not respecting your trading rules, c) not sticking to your plan.
2/ Lack of knowledge—Inadequate understanding of the market, trading strategy, financial instruments, and fundamentals can lead to poor decision-making.
3/ Not having a mechanical trading system—This leads to emotional trading. Decisions driven by emotions like fear and greed rather than rational analysis result in significant losses.
4/ Overtrading—Taking many trades will affect your decision-making ability and lead to poor decisions.
Apart from these reasons mentioned above, a person can lose money due to other reasons. For example, there may be a sudden global collapse while trading or there may be some natural cause. As an example, I can share my experience. Ukraine and Russia went to war while I was trading. I also lose profit from my potential field. Again, during the Corona period, there is a collapse in investment. Apart from people like me, many experienced people will also fall victim to this collapse.