Spoilers for Good Omens Season 1 ahead. Although it takes many people to stop the apocalypse in Good Omens, the witch Anathema Device plays one of the most important parts. As the last descendant of Agnes Nutter, she uses her ancestor's prophecies to save the world. But when more nice and accurate predictions of the future appear on her doorstep the day after the supposed Armageddon, she makes the bold decision to destroy the new prophecies. She doesn't state why she does so outright, but it seems to be an effort to take control of her life — after years spent beholden to a book that told her the future, Anathema wants to start creating her own destiny.
Anathema has lived her entire life following The Nice and Accurate Prophecies of Agnes Nutter, and though she struggles to detect that Adam Young is the antichrist, she does successfully interpret Agnes' highly specific predictions to help save humanity. She has great regard for her ancestor and all she's passed down to her, but when Further Nice and Accurate Prophecies of Agnes Nutter Concerning the World That Is To Come, Ye Saga Continues gets delivered to Jasmine Cottage, Anathema is understandably fed up.
So, just as Agnes had been burned at the stake, Anathema and her witchfinder boyfriend, Newton Pulsifier, burn these new prophecies. When Newt asks if Anathema feels OK with this major decision, she says, "Yes, I'm sure. I know what I'm doing, I just don't like it." And in response, Newt offers this tidbit of advice: "Think of it this way, do you want to be a descendant all your life?" Yes, Anathema knowing when the end of the world was coming and how it would happen came in handy, and there will certainly be more wars to come. But Anathema wants to define her own destiny rather than constantly looking to the future.
In the Good Omens book, Anathema doesn't explicitly destroy the prophecies. Once they're delivered, she goes to read them. However, Newt stops her. "Think of it like this," he says quietly. "Do you want to be a descendant for the rest of your life?" The rest of their story ends, "She looked up. Their eyes met."
But in the Amazon series, Anathema is given the agency to make this choice on her own. There's no question about her intentions: she will not be a descendant anymore. This goes against her prewritten destiny — hell, even her name, which means "a strong curse." And while it means she'll no longer be able to foresee or stop any impending crises of humanity, it gives her the peace to follow her own path in the present.
Anathema's choice is a difficult one to make. But even if you don't agree with it, you can empathize with a woman who has only lived life according to thousands of prophecies from an ancestor she never met. Plus, it's not like Anathema is solely responsible for the fate of the world. Aziraphale the angel (Michael Sheen) and Crowley the demon (David Tennant) are sure to be around for a few thousand more years now that heaven and hell have agreed to leave them alone. So while the witch and her witchfinder can write their own story, Good Omens leaves it to the angel and demon to keep looking after the world.