Over the years, I’ve often been reminded of my grandmother’s words. Recently, while I was reading Ian Buruma’s new book, “Stay Alive: Berlin, 1939-1945” (Penguin Press), they played on repeat. Buruma is a writer who grew up in the Netherlands. In the opening pages of “Stay Alive,” he recounts the story of his father, Leo, whose experience was, in key ways, the mirror image of my grandmother’s. Leo didn’t flee Berlin to escape the Nazis; he arrived there to work for them.