I occasionally have a bout of insomnia and it is The Worst. I'm not sure what causes it; I'm not anxious about anything in particular. But the second my sleep is disrupted I become anxious about THAT. Am I going to get enough sleep tonight? Oh no, I've woken up and I'm anxious about that! I only have so many hours to be able to magically cram in some more precious sleep! Ah, yes, I can feel myself going to sleep! HOW EXCITING! Aaaaaaaaaaaaaaaaaand....Now I'm awake again. It's vicious loop!