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(THE CONVERSATION) Each year, in the final few hours of the last day of December, many people all across North America gather with friends to raise a glass and sing Robert Burns’ famous ballad, “Auld Lang Syne.” Standing at the brink of a New Year, arms around each other, they ask: “Should old acquaintance be forgot, and never brought to mind?”

The question is meant to be rhetorical, of course – the answer is “No.” The years may pass, but we should hold on to our friends.

For many...