We had both had previous relationships, but this was the only one Viv cared to describe. You could say I’d been duly warned.
-- Narrator (Part 1, Chapter 1)

Importance: It is because Viv told Donald only about her previous relationships with horses that he felt he should have known how serious her fascination with horses was. After the fiasco with Mercury, Donald believes he did not pay adequate attention to what she was trying to tell him.

I tried to make up for my lack of enthusiasm by being a good listener. But there is listening, and listening. When my patients talk during an exam, I respond appropriately even when 90 percent of my attention is focused on the cornea, the iris, the lens. And that, I fear, is how I listened when Viv first told me about a horse named Mercury.
-- Narrator (Part 1, Chapter 1)

Importance: Donald describes a habit of his, in which he manages to respond properly to...