Forgetting, according to the theory, is not something that just happens, it's an active process.
Well, that's the theory, but we all know, we don't always mean to forget. Sometimes there are more important things, or more interesting, for us to remember. And sometimes our brain does the forgetting for us, without our wishing it.
The old lady wondered why the car we were in was so big. "It's a hearse. We're going to the funeral, do you remember?" "Whose funeral is it?" "We're going to bury Dad, your husband." "My husband? I was married? Was he a good man?"
She had not chosen to forget the life they had spent together. Her brain had simply switched off those years as if they had never happened.
Lucky in a way. What would her life have been if she had remembered those seventy-three years and had nothing to replace them? Worse still, if she had had to start remembering all over again?
Thanks to commenters who have seen the point of this one. We had always thought she would be desolated if he went first, and even though she had forgotten who we were, at least she recognised us as friends.