What even is sleep ?

2 weeks in now! She sleeps all throughout the day and nothing throughout the night. I’ve been struggling as a postpartum mum to get my emotions and feelings together aswell. I’ve only just come across something called “sundown anxiety” and I’ve just diagnosed myself with it. The feeling of knowing the night is about to come just makes me feel so overwhelmed. I know that I’m about to have such a tough night ahead of me. Does anyone else have this? if so, how are you coping? or how did you cope with this ?