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If you look into your own heart, and you find nothing wrong there, what is there to worry about? What is there to fear?

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When you know a thing, to hold that you know it, and when you do not know a thing, to allow that you do not know it - this is knowledge.

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Study the past if you would define the future.

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Think of tomorrow, the past can't be mended.

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To know what you know and what you do not know, that is true knowledge.