In his interview with Stephin Merritt in The New York Observer, Philip Weiss records this exchange about the song [source]:
I told Mr. Merritt I sang it to my wife (trying to imitate his deep sad tones). He looked at me like I was crazy.
"The song is tragic and pathetic. 'When you cancel dinner plans, I wish I didn't understand'?" he said. "It's a declaration of love for someone who doesn’t return it."
"It's a song about separateness in a relationship," I said. "My wife cancels dinner plans—so what."
- [Lyrics and guitar tab] from stephinsongs web site.