About to lose my beloved dog of 16 years this Friday

The anticipatory grief is absolutely horrible and I have no idea how to cope. This is Sammy, my sweet Shih Tzu that I've had since I was 8, I'm 24 now. I've had him my entire life and now he'll be gone on Friday. He has advanced kidney disease, dementia, and likely cancer as well, and the last thing I want is him to suffer anymore. :(

Edit: Thank you all for the immense love and support, it means so much to me ❤️❤️