Relationships are give-and-take, and when you're a tennis player, you're certainly not giving. You have to be self-absorbed. It has to be about you.
I studied Hitchcock a little bit at University and knew the famous story about the Birds - that he'd tortured Tippi for a day using real birds. I had no idea that it was a five-day onslaught and that it was the tip of an iceberg that carried on through to another film.