Textbooks are nothing to the whole high school content, but you must learn well, because the foundation is very important to the whole high school competition, such as triangle deformation. If you really want to be a good MO member, you should practice until you can see what is after 3 or 4 steps with your eyes.

There are three key points in the high school mathematics competition:

To understand something about universities, we should fully grasp the minimum Cauchy inequality, derivative formula, number theory related content set theory and related skills in modern algebra.

Second, conditioned reflex. This can only be done by training the roots of the competition at ordinary times. After all, different methods are too clever and flexible, but there are methods for training. That is to do all the problems you encounter at least twice. If not, it must be done at least three times to reach the conditioned reflex level. Of course, you must do it once in a while. This process is painful, but effective. IMO and those people do it.

The most fundamental thing is that you must fish for three days and dry the net for two days, and you will accomplish nothing.