"In a threesome, there must be a teacher." It has become a famous saying throughout the ages and has been passed down to this day, and it is well known to women and children. Confucius believes that when three people walk together, there must be a teacher. The advantages of others are definitely teachers worth learning, and the shortcomings of others are mirrors worth warning. So he is also a teacher. Remind people to learn from the strengths of others at all times, so as to improve their moral cultivation, find out the shortcomings of others, and check whether they have the same problems for themselves, and if so, correct them in time. Make one's behavior conform to the principle of being a man.