I went through a very similar experience with my dog who was my best friend. It's been a couple of years now. He also had terminal cancer around the same age. If you need anyone to talk to who can relate, hit me up.

It hit me pretty hard and had me down for a long time. There have been a few things I came to realize while recovering from the grief that I wanted to share.

The first realization that helped me was understanding that I did the right thing letting him go and not making him suffer from cancer. I felt a lot of guilt because I made his last appointment. I don't know if you've felt that or might feel that, but know that you're doing the right thing, it's just a very hard thing to do and it makes you an even better person for doing it.

The second realization was that my pup would have wanted me to be happy and that I can choose to honor him through my happiness. This one actually came to me in a dream about my pup where he let me know "life is for the living" and that he'd rather me be happy

The third, and probably most powerful, realization was that the life I gave him was one of the most beautiful things I can comprehend. We all have our time here and then we must go. I feel so unbelievably honored that I was able to make his time here as amazing as possible. He spent his whole life being extremely loved and able to give that love back. He didn't have to suffer the cancer, or suffer aging and deteriorating. From start to end we were able to make his life amazing, and it sounds like you did the same for your pup. You should be incredibly proud of that.

I still miss him terribly and think about him all the time, but when I think back now I feel incredible pride and happiness. Make sure you get some keepsakes to cherish, we did some plaster paw prints and also cut some of his hair to keep (maybe weird but I don't mind that.) The keepsakes gave me some comfort and helped me process everything.

My heart is with you, let me know if you need anything an internet stranger can provide <3