Time. I'm still a nervous wreck and if I hear something unusual I am up with a flashlight checking on everyone. But you get used to it over time. In the same way that parents with children have nightmares, I feel the same way about all my animals.
Also - I had a dream that someone developed plastidip safe for hedgehogs and breeders started diping hedgehog quills in the plastidip and on the points they would form balls like on hair brushes so hedgehogs looked like hairbrushes when all quilled up. It was weird.