Being able to understand and know others is called wisdom, and being able to know and know yourself is really smart.

Source: Chunqiu Lu Laozi's Tao Te Ching

2, the original text: black hair does not know how to study hard early, but regret learning late.

When I was a teenager, I only knew how to play and didn't know how to study hard. When I was old, I regretted why I didn't know how to study hard when I was young.

Source: Yan Zhenqing's Persuasion of Learning in the Tang Dynasty

3, the original text: I save myself three times a day: I am unfaithful to others? Don't believe in making friends? Can't get used to it.

I will reflect on myself many times every day. Did I do my best for others? Is it honest and trustworthy to associate with friends? Have you reviewed what the teacher taught you?

Source: The Ten Analects of Confucius in Pre-Qin Dynasty

4. Original text: Get inspiration from doubt and get happiness from bitter life.

Translation: The truth that is understood is often thought out from problems. Happiness is often acquired after suffering.

Source: Qing Shen Juyun's "Xi Yan Yu"

5, Confucius said: "See the sage Si Qi Yan, see the sage and introspect."

Confucius said: When you see a person is virtuous or talented, you should think about learning from him. When you see a person without virtue, you should reflect on whether there are any mistakes like him.

Said by: Confucius in Spring and Autumn Period, Analects of Confucius, Liren.