I don't know the exact reason, but I think it's because I become alone in an enclosured space with my own thoughts. 

I play music to mitigate it, but guess what? I get my mind ridden with doubt when I have to choose a song/playlist too! Like I want to choose a good enough one to relax, but I have a feeling of "But you've heard them so many times already, so why would you choose?"

Ironically, showering is something I feel necessary for going to sleep. If I don't, I feel dirty and I get more trouble falling asleep.

I know it's a bit weird and specific, but if you could give me some advice I would really appreciate it! 😄