Waiting for the end

My dad has a matter of days to weeks. I'm visiting him in the hospital every day, talking to him, but every day it's this agonizing dread of knowing I'm about to be hit with the worst pain of my entire life and a loss I'll feel for as long as I live. How do you cope with that? I want to scream, I want to beg this to stop, I want to be told that we've all ridiculously overreacted and he'll be home from the hospital as soon as he feels better, part of me wants to just rip the band aid off and have it over already, part of me wants to keep doing this every day for years as long as it means he's still here... anything but this aching dread of trying to get through each day knowing the pain of a lifetime is hanging over me like the sword of Damocles. I know this is something so many people go through but I don't know how they get through it.