This November, for the first time in 25 years, my husband and I traveled back east for Thanksgiving. It’s not that we don’t visit family a few times a year, but it always seemed that traveling from Los Angeles to Boston on one of the most heavily traveled weekends of the year was a recipe for disaster. But this year, since my mom decided she and my dad could no longer make the trip to her brother’s for their normal celebration, my sisters and I decided to bring Thanksgiving to my parents. Paula, my sister from Connecticut, brought a 26-pound turkey and 12 pounds of roast beef. Carla, my sister in New Hampshire, made enough desserts to fill a football stadium. We had 14 people for dinner, ranging in age from 17 to 83. Observing the differences in the thoughts and activities of three generations during a full-day celebration was like watching three genres of movies simultaneously. At one point, I noticed my 17-year-old niece and her cousin sitting next to each other on the couch,...