I’m greeted at the door by my friend John. "Hello, John. Happy birthday," I say, trying to match his smile with my own. "Great to have you here, Leo," he replies, leading me down the hallway. Laughter spills from the living room. *I must be one of the last ones to arrive*, I think to myself. As I walk in, I see familiar faces—John’s friends, all around my age—wearing party hats and helping themselves to food laid out on t...