Losing my cat tomorrow. I've never felt anything like this before

My cat is 16. She's been quite sick for about a month now and it is her time to go. Earlier today I scheduled the appointment for at home euthanasia (hardest phone call of my life probably?). The vet is coming tomorrow afternoon. I'm just sitting here and looking at her, sleeping next to me in her bed like always, and I can't believe in 24 hours she just... won't be there anymore? I'll never see her again? Never pet her again, never hear her meow or purr again? Never have her fall asleep on my chest again? It's the most surreal feeling, it almost feels like I'm dreaming all of this up. The thought of getting up in the morning or coming back home at the end of the day and not seeing her in her usual spot is unfathomable. I just genuinely don't know how I'm going to do this. :(