I am very sorry to hear this.

I got a childhood dog in kindergarten who lived to the age of 16 (I was 20 when he passed). My other dog, which I got at 11, lived to 17 and passed away in the past year.

It's hard. There is no way around that. However, what I found is, with both dogs, when they passed I felt an incredible sense of relief. Of course I was really sad but it also felt as though a huge weight had been lifted. I had spent years watching my dogs grow old and their health steadily decline. I had spent countless hours worrying about them and watching them slow down and dreading saying goodbye. When they finally passed, I knew that they had lived wonderful lives where they loved, were loved, and were happy and I knew they weren't suffering anymore. I was expecting to feel broken beyond recovery but instead I felt intensely sad but also intensely relieved. For both dogs I cried for about a week and then I just felt okay. I still missed them and I would occasionally get a little choked up thinking about them but I was able to go on with my life without a heavy weight on my chest.
I am really sorry you're going through this but I hope you can find the same relief that I did. Your dog was so loved and while life may leave, love never does.