Be modest and prudent, never lag behind!

谦虚谨慎，永不落后！

《新英汉大辞典》

Girls' ability never lag behind the boys' ability.

女孩的能力永远不会落后于男孩的能力。

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Now many years have passed, I keep telling myself that I can do, I will never lag behind the boys.

现在许多年过去了，我一直告诉我自己，我可以做，我永远不会落后于男孩。

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Despite the fact that for the best part of two centuries China came to suffer hugely at the hands of the West, and to lag badly behind the West, the Chinese never stopped believing in themselves.

BBC: A Point Of View: How China sees a multicultural world