ACKNOWLEDGEMENTSAuthor: Dr Nguyen Dong Hung - pen name Minh HungAs I write these lines, I know that the book you are holding is not only the result of many years of reading, practicing, and teaching, but also the crystallization of many hands silently supporting, of many patient eyes examining, and of the trust sent from many people. Therefore, "thank you" is not just a ritual of closing the book, but also the way I bow my head to the grace of life.First of all, I would like to thank my ancestors who sowed the seeds of wisdom on the land of Tu Binh: the ancient books, the fortune-tellings, the debates and annotations over the centuries have given me a language to talk about the map of human energy. Without them, there would be no path for me to follow, and certainly no "Eight Character Essence" to share.I would like to thank my teachers, seniors, and friends in the Oriental Studies research community - those who have not hesitated to debate, question, and criticize to the core of each argument. The times of being "questioned" have helped me learn to be humble before the truth, not to cling to formulas, and to persevere in finding a common voice between classical and modern.Thank you to my readers who have opened their horoscopes as if they were opening a door to real life. Each story, each journey of transformation, each candid feedback has made this book less abstract, more accessible - down to earth - applicable. I always remember: knowledge only truly lives when it lives with people.I would like to thank the team of editors - researchers - proofreaders - designers - editors - printers. From the first draft to the finished book is a long journey of words, punctuation, spaces, graphics... Every edit, every "suggestion to cut" or "please explain more" helps the book get closer to the readers, keeping it standard yet warm.I would like to thank my family, parents, spouse, and relatives for giving me the foundation: peace to work, space to be calm, and confidence to move forward. The late meals, the postponed appointments, the days when I "spent more time in books than in real life" were all supported by love and understanding. That is the most precious Dac The in my life.