There are three kinds of reading, namely, heart, eyes and mouth. If the heart is not in the book, then the eyes will not read it carefully. Because of inattention, I can only look casually and never remember. Even if you remember it, it won't last long. "Heart to heart" means heart to heart, "eye to eye" means reading a book carefully, and "mouth to mouth" means reading it. Of the three, heart-to-heart is the most important.