Both oil producers and miners recall painful lessons of previous decades when low prices were the norm.

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Banks are highly regulated and have learned some painful lessons over the years.

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We have turned prejudicial blind eyes to injustices against some groups and have learned painful lessons in the aftermath.

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And now, as then, the productive class of our now gigantic, colony-turned-superpower, learn and teach again, the painful lessons of history.

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One of the more painful lessons all investors learn is that a 20%-40% loser in your portfolio can offset the nice gains from the other holdings.

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The markets teach us all painful lessons.

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Former Soviet-dominated states in Eastern Europe, Some European states learning the painful lessons of the collapse of the welfare state, South American nations which are breaking away from left and right wing populism, parts of the long-suffering continent of Africa, Asian city states with low margins for error, swaths of the world are embracing as precious what we throw off as threadbare: economic liberty.

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If a company launches its efforts too soon, it may suffer unnecessarily through the painful and expensive lessons associated with deploying an immature technology.

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Winfrey also guided us through the painful experience and lessons learned when her Leadership Academy faced a distressing, and highly publicized crisis in 2006.

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As for the news business, the lessons have been painful.

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