2, too careless, maybe I don't think this is a topic I usually don't do, and I made mistakes in the exam because I accidentally read the wrong question, miscalculated the number and so on.
3, it may be that the knowledge structure is not perfect and the knowledge is not clear. I wonder if you will feel this way. When you learn a chapter, you know how to use what you have learned in this section, so you do well. When you take an exam, you don't know where to start. This is a problem that your whole organization is not clear about. You need to sort out what you have learned regularly and consider how they are related and how to go from one step to another.
That's about it. If you feel that there is no psychological problem, the latter two points are more likely and easier to overcome. Come on ~ ~ ~