What is the fundamental reason why Prime Minister Zhang doesn't know his own handwriting?

Prime Minister Zhang doesn't know his own handwriting. If he answers in the original text, it means that Premier Zhang is a good writer and is useless. At that time, everyone laughed at it. The prime minister is calm. This fable tells that there was a prime minister named Zhang Shangying in the Song Dynasty. His hobby is calligraphy. He especially likes writing cursive script. Pick up a pen when you have nothing to do, and you are very proud. In fact, this painting of the Prime Minister's calligraphy is far from home and its handwriting is inappropriate. At that time, many people laughed at him, but he didn't agree. He still goes his own way and writes according to his old habits. My nephew had to guess and was cheated. But in some places, he really can't understand, and he doesn't know where to disconnect. He had to stop writing and ask Prime Minister Zhang with the manuscript. Prime Minister Zhang took his masterpiece and read it carefully for a long time, but he couldn't recognize it. He doesn't even know his own words.