Zhao Mengfu said: "It is not easy to use a pen through the ages, because time has changed." What do you mean?

I understand the meaning of this sentence: if the structure of the word is beautifully written, it will not be easy to stay in the world; And the pen (refers to the strength of the pen, the direction of the force and its changes, generally refers to the spirit of the word), if the level is high, it will take a thousand years to meet one. Generally speaking, this sentence means that using a pen is more important than structure and more difficult to master. Both the structure and the pen are high-level calligraphers, and only one will appear in 1000 years. For example, Yan Zhenqing has been away from us for more than 1000 years, and no one has surpassed his calligraphy level.