2. Even the most sophisticated person can't see his own back. -Africa

3. The most difficult thing is to know yourself. -Greece

4. Self-respect, self-consciousness and self-control can lead to the lofty realm of life. -Tennyson

5. Self-knowledge is the most rare knowledge. -Spain

6. Complacency, arrogance and credulity are the three reefs of life. -Balzac

7. You know where your shoes are tight. -Spain

8. You know what you eat. -Soviet Union

9. Clean yourself with a clear spring. -Tang Hanyu