Christmas was always one of the best times of the year for our family. Growing up on an Army base in Germany, the odds of having at least a few inches of snow in December were pretty good. School would be on hiatus for a few weeks, so my brother and I and our friends would make the most of the shortened days on the sledding hill behind our apartment block, a doubly sloping expanse with an enormous pear tree sticking out of it. The lot of us would trudge up and propel ourselves down again and again, until the hillsides were stripped bare of snow. As evening fell, my brother and I would head...