Vonnegut on moral character

I'm thinking about re-reading Mother Night. I've gone a while without a Vonnegut fix. I pulled it off the shelf this afternoon, and discovered the opening paragraph of the introduction, which I'd forgotten:

This is the only story of mine whose moral I know. I don't think it's a marvelous moral; I simply happen to know what it is: We are what we pretend to be, so we must be careful about what we pretend to be.

I think it's a marvelous moral. I should definitely re-read this book.