Maybe the reason why we can never go back to the past nor to even attempt to recreate every single thing that happened without mistake is because everything will keep on changing—the universe, the world, the weather, even the very nerves of ourselves.
It's not us anymore, the world isn't that world we know anymore—it's all just reflections of what we used to be, it's just a variation of yourself, and today, you're a different you, no matter how much you think you're not.
