Why did Wen Weiming become a calligrapher?

Wen Zhiming wrote A Thousand Words, at the rate of ten books a day, and the books made great progress. I have lived in books all my life, and I have never hesitated, or simply answered people, and I have never taken pains again and again, so the older I get, the more subtle I am.

Translation:

Wen Zhiming supervised the writing of Wenziwen, with ten books written every day as the standard, and calligraphy made rapid progress. He has never been careless in writing all his life. Sometimes answering people's letters is a bit incomplete. I must have rewritten it three times and five times, not afraid of trouble. Therefore, the older he is, the more exquisite and beautiful his calligraphy becomes.