In psychology, they say there is a magic number-you have to read a book at least seven times before you can understand its essence. If you listen to a lecture, you have to hear it several times before it can alter your viewpoint and behavior.
心理學上有魔術數字的說法，讀一本書至少要讀七遍，才能瞭解精華；聽演講也要聽好幾遍，才能進而改變觀念和行為。