I have a terrible for memory for most things, including what I've written. So this comment from Salman Rushdie, about repeating himself unintentionally, really hits home..
My Danish translator emailed me very politely and said, ‘You know on page 215 of your novel such and such character says so and so. And as you of course remember in your previous novel, such and such on page 107 this completely different character said the same thing. I'm really interested to understand the inter-textuality and why it was that you wanted to connect this character to that character?' And then you pretend you did it on purpose. You can't just say ‘oops’.