ON TUESDAY, I turned 72. In Eugene, this feels less like a milestone and more like a quiet transition from being a participant in the frantic race of life to becoming an observer of it, much like watching the rain — or perhaps the joggers — pass by my window. There is a specific, strange alchemy to this age: a mix of profound gratitude for simply still standing and the melancholy of watching cherished, long-held certainties fade away.