Not to mend one's ways when one has erred is to err indeed.
If proper in their own conduct, what difficulty would they have in governing? But if not able to be proper in their own conduct, how can they demand such conduct from others?
An inch of time on the sundial is worth more than a foot of jade.
The archer who misses his mark does not blame the target. He stops, corrects himself and shoots again.
To know is to know that you know nothing. That is the meaning of true knowledge.
Listen widely to remove your doubts and be careful when speaking about the rest and your mistakes will be few.