This is the highest realm of calligraphy! Calligraphy has no highest realm, because everyone's realm is different. I think writing your own realm is success, and then you will constantly improve yourself.
As for what I forgot, passion and so on. I personally feel unreliable. It is possible for Mr. Zhao Puchu to forget what I forgot, and he also forgot that he wrote calligraphy works, but I think passion is impossible. Nowadays, calligraphers often have passion (perhaps the skill of making wine), and what they write is not his own, but something that gets carried away.
In the past, calligraphy was a tool of books. People like Mi Fei and Yan Zhenqing were few and far between, but can you say that Mi Fei and Yan Zhenqing are the highest realms? Never seen it!
At present, at the beginning of the founding of the People's Republic of China, Mr. Guo Moruo, the world's first running script, also questioned this and thought that Lan was bravely forged. From Zhi Yong's calligraphy works handed down from generation to generation, I personally felt the foundation of Lao Guo's suspicion.
Personally, I feel that Yan Zhenqing's "Sacrifice to My Nephew" is as good as Lanting's, and it is also a portrayal of Yan's mood at that time, so "the writer is like this!" It is the highest realm of calligraphy.
Books are like this!
Is it simple? Is it still difficult?