People are sharp in spirit when they are young, and their thoughts are easily dispersed when they grow up. Therefore, we should educate our children as early as possible and don't miss the opportunity. When I was seven years old, I recited "Lingguang Dian Fu". To this day, I look back every ten years and have never forgotten it. After the age of 20, the back sutra was left there for a month, and it was abolished. Of course. People are always in trouble, and when they are in their prime, they lose the opportunity to learn. They should seize the time to study in their later years and not give up on themselves. Confucius said, "You don't make a big mistake when you learn the Book of Changes at the age of fifty." Wei Wudi and Yuan Yi, who studied harder when they were old, are both examples of diligent study since childhood. Ceng Zi began to study at the age of seventeen and finally became famous in the world. Xunzi began to study in Qi at the age of fifty, and still became a great scholar. Gong began to read Spring and Autumn Annals in his forties and finally became prime minister. Zhu Jun didn't learn the Book of Changes and The Analects until he was forty, and Huangfu Mi didn't learn the Book of Filial Piety and The Analects until he was twenty. They all became great scholars in the end. These are all examples of early addiction and late awakening. It is too late for most people to start learning when they are adults. Getting along with each other day after day is like standing on the wall and seeing nothing, which is stupid enough. People who learn from childhood are like the light of sunrise; People who start learning when they are old are like walking at night with torches, but they are better than those who can't see anything with their eyes closed.

"Smell" should mean "listen". I don't understand the second question.

This passage tells us that one should "learn early"; If "lost in the prime of life", then "especially the study that night, don't give up." This paper mainly discusses an optimal learning age.