Why does "Let's Swing" have a faint sadness?

Because the depiction is too pure and beautiful, and there is too little of such beauty in real life. When you say goodbye to your student days and face all the constraints of the world, that kind of simplicity and openness will never come back. For more specific psychological activities, you can refer to a description in the web article "Dragon Snake". Wang Chao's soulful purple woman figure appeared on the screen, every shot, a talk, an action, are so vivid, a thousand times y printed in the deepest part of Wang Chao's heart, never wear out. Looking at this image, Wang Chao seemed to forget everything, and recalled the scene three years ago, at the Heavenly Star Lake, following Tang Zichen to learn the art. Every scene, every image, flashed clearly in his heart. He walked the water tank, hit the sandbags, and fell to the point that his body was lightly swollen, it was Tang Zichen who carefully rubbed the medicine every time, and used acupuncture to spread this bruise. He shook the big gun, every time he shook his arm sore, but also Tang Zichen helped himself to knead and relax the tendons and bones. She corrected and corrected each of her boxing stances. Every phrase of the practice of kung fu was explained in detail. During those two years, it was almost always Tang Zichen who took care of herself in terms of food, clothing, and housing. In Wang Chao's feelings, Tang Zichen was like a biological big sister loving her weak brother. Such feelings erupted all over Wang Chao's heart after seeing that familiar figure on the screen. "Your brother has grown up now, do you know that? But your younger brother hasn't been able to reach your heights, and hasn't been able to pass on your boxing skills ah." Wang Chao muttered in a voice that only he could hear, his face seemingly happy or sad. His thoughts, in the end, stopped at that evening. The afterglow of the sunset in the end, ah, shone the entire Tianxing Lake sparkling. Swinging his oars, he gently floated the boat to the center of the water. Tang Zichen stepped on the water, floating away. At that moment, Wang Chao thought he would never see her again. At that moment, in Wang Chao's heart, this sister of his was the immortal in the sky, who came down to enlighten himself. On that day, that familiar, crisp, pure child's voice song, forever floated in Wang Chao's heart. "Let's swing our oars, the boat pushes away the waves, the water reflects the beautiful white tower, surrounded by green trees and red walls, the boat gently, floating in the water. Blowing on the face, the cool wind ................" The child's song, is so bright and clean and cheerful, without a bit of dust. The things in the world are like the voice of a child. If they were all like a child's song, so bright, pure and innocent, how wonderful it would be. At the moment before Tang Zichen left, Wang Chao's heart was just like a child's. "We are all just mortals, no matter how high our boxing skills are, how skillful our techniques are. It's still necessary to be rolled into this rolling red dust. Perhaps, what you meant was to leave a legacy and let the martial arts skills slowly and smoothly pass on. You have said many times that we are not from the same world, and that you don't want me to get involved in that world, to live a lifetime, to live peacefully. However, I am now gradually stepping into your world as well. In this world, there is no longer a child's cheerful, clear, carefree song. I may have failed you." The child's bright and pure singing voice, Tang Zichen's immortal shadow, the red dust's hooks, killing and bloodshed, money, power, and temptation. All mixed together, filling Wang Chao's mind.