When I was a teenager, I invented a ritual. Before a really exciting party or a big test or summer camp, I would take a moment while sitting on the toilet and think: you will be back here again later today, or tomorrow, or in three weeks, and it will look exactly the same, but you will have changed. Something will have happened to you. And, sure enough, when I’d return, I’d sit in the same place and take stock of the familiar things — the white wicker hamper in front of the toilet, the bath tub to my right, the sink to the my left — and marvel at how they had not moved even an inch while I was off doing new things, meeting new people.