No one ever tells you that begging for a dog as an 11-year-old could affect you deeply as an adult. They just make you promise to clean up after the animal. But when Rainbow was 10, my parents moved abroad, and she came to live with me in New York. At first, she couldn’t figure out how to pee on concrete; she cried a lot, so I cried a lot. Eventually we learned how to communicate, even as she lost her vision, her hearing, her continence.