The physical and mental development of modern young people is different from that of their predecessors in at least the following five ways. The reason is that the domestic society has changed more than other countries in the past 30 years. 1. The duration of puberty is uncertain The definition of puberty in psychology. It is not based on a uniform age, but on the degree of individual physical, psychological, and social development. The lower age limit of puberty begins with the maturation of the individual’s sexual organs, and the upper age limit ends with the maturation of mental and social development. This shows that adolescence can be very different not only between the sexes, but also between individuals. Some enter adolescence in the middle grades of elementary school, while others have not yet begun by the end of middle school. The upper limit of puberty is even more inconsistent, with the upper and lower age limits changing in modern times, from between 13 and 18 years at the beginning of the century to between 11 and 21 years now. The extension of the time limit of puberty makes the physical and mental changes during puberty increase, and also makes the factors of instability during puberty increase. 2. Imbalance of physical and mental development Due to the extension of the upper and lower limits of puberty in modern people, the physical maturity of young people in the past was later and the psychological maturity was earlier, while the physical and mental development of modern young people is on the opposite trend. In the last hundred years, the average age of female menarche in Europe and the United States has advanced from 16.5 years to 12.5 years, about four months earlier every decade. In the past, life was difficult, and children participated in adult life from an early age, engaged in production, and some were required to take responsibility for family life in their teens, so it was inevitable that their mental maturity was earlier. Today’s young people, as a result of their early physical maturity and late mental maturity, have an imbalance in their physical and mental development, and their mental ability is unable to control the impulses derived from their physical maturity, which is the root cause of the increase in youth behavior problems today. 3. Growing up in a discontinuous culture In traditional agricultural societies, human culture is continuous, its interpersonal relationships are less variable, and its lifestyle is stereotyped. In addition, in terms of behavioral norms, moral standards, value judgments and even religious beliefs, they have been passed down from generation to generation and have remained unchanged for a long time. Therefore, in the past, the new generation grew up in the footsteps of their parents, and the problem of “generation gap” could not arise. With the industrialization of cash cities, social diversification, and the loss of cultural continuity, the environment in which fathers and sons, and even brothers, live may be completely different. Therefore, when the new generation grows up, it is inevitable that parents cannot teach their children, or brothers and sisters cannot teach their siblings, in terms of life and knowledge. As a result, it is conceivable that the phenomenon of cultural discontinuity will have a negative impact on the growth of the new generation. For young people growing up in today’s society, with the diversification of society and the popularization of education, there are more opportunities and choices for their future development. At the same time, due to the opening of society, young people have more freedom to choose gender and marriage than before. However, both of these choices require ability, and the ability to pursue and make appropriate choices is not easily available to young people who have grown up in a discontinuous culture. As a result, most of the young people are confused about their future in the paradoxical situation that there is a wide range of objective prospects and insufficient subjective conditions. 5, do not realize that they are in the blessing Because the objective situation and subjective feelings of modern young people are very different, the impression that young people nowadays do not know the blessing in the blessing; that they grow up in a superior environment, but do not know how to use the conditions in the environment to strengthen themselves. The young people of today do not know that they do not know that they are in a fortunate place. Because “know the blessing” will “cherish the blessing”, know the blessing is to rely on life experience, modern young people are free to experience the life of open mouth to eat, stretch out hands to wear clothes, naturally do not appreciate the value of learning. Even, for some young people who have been spoiled since childhood, they are likely to regard the “blessings” that others say as “burdens”.