Forty without confusion comes from Confucius' Analects of Confucius, which means that you are determined to learn at the age of fifteen. Fifteen years later, according to his rich experience and life training, he reached the "thirty-year-old".
Basic explanation
He said that at the age of fifteen, he was determined to learn. Fifteen years later, this period was the golden stage of his life, and he was thirty years old. In the best physical condition! (Li: Gao, the best time of life, it means that people have passed noon for 30 days)
"Forty without confusion", forty years old, not confused by foreign objects.
At fifty, you know your destiny. At fifty, you know the laws of nature. (Life: Law, Law)
"Sixty means obedience". When you are 60, you can listen to different opinions.
"At the age of 70, I can do whatever I want, and I won't do anything out of line".