When I was 10 years old, trauma arrived quietly, through the voice of my pediatrician. I was out of school that morning with a toe infection when the doctor walked into the exam room and told my mother and me that a plane had hit the World Trade Center in New York City. At 10, you live in a world that is small and immediate. Barely a week earlier, we had spent Labor Day weekend at my grandfather's home at Candlewood Lake in Connecticut, sailing, cooking and living inside the sweet, unthinking comfort of an entirely ordinary weekend together. That morning in the doctor's office, my mind did not connect the news to the fact that hours earlier my dad had kissed us goodbye at our Greenwich home, driven to Newark Airport and boarded an early-morning flight to San Francisco to visit his brothers.

My father, Donald Greene, was on United Airlines Flight 93 on Sept. 11, 2001. Unlike the jets that struck the World Trade Center and the Pentagon that morning, Flight 93 never reached its target. Aware that their plane had been rerouted by terrorists toward Washington, the passengers and crew mounted a counterattack in the sky. During their fight to regain control, the plane crashed into an empty field in Shanksville, Pa. Those on board sacrificed their lives to prevent even greater catastrophe.

In the quarter-century since that morning, my family's ritual of remembrance has taken us to that rural field. Today, the site is a soaring national memorial, where visitors walk the ground where 40 ordinary people chose extraordinary bravery. As we mark 25 years, I find myself grappling with a different kind of grief — not for my father, but for the country we once were.