As for why you make mistakes in doing the problem, it's because you take it for granted. If you get rid of the habit of taking it for granted, you can definitely go to by going up one flight of stairs.
If the perfect score is 150. You can only take 70-80, which I recommended you to take.
First: write the test paper quickly (if you think it's easy, do it yourself). Giving up is a little complicated, don't do it yet)
Second: See how many points you have made. If you can reach 100, you will be ok! Then think about these questions carefully and make sure they are correct. (Note that you didn't say you could get 100. This 100 point is just a measure in your own mind. )
Third: since everything that can be done has been done and checked, what cannot be done can also be done. Write in a certain format. Can do a little is a little. So your grades will definitely not be too low. At least 100!
Personally, I came from the bottom of my class in mathematics, that is, every exam is 20-40 points, and every exam is close to full mark, so I personally think it is worth recommending some methods to learn mathematics! )
If you want to improve mathematics fundamentally, there is no other way except one word: "practice"!
Of course, this practice is still problematic. The first is to do some topics that suit you, and then do some difficult ones. Don't rush to see the answer, it's no use to you! Think at least one question a day. Then I still can't do it Go and see the answer. However, especially the questions that can't be done don't really look at the answers. You need to spend more time thinking. The answer comes from this, not the process of solving the problem, but the idea. Why didn't you think of that yourself What is the essence of this topic? What is the premise of this idea? This is the key, so that you can solve many similar problems at the same time!
Record some questions and answers with a notebook! Why? Because these topics are your ideas for solving difficult problems in the future, this is called divergent thinking.