God, I remember when I had to have my cat put down...so long ago now. She was already old, and suffering from kidney problems, as old cats do, but a dog chased her, and her tendon snapped. Had to have her put down. I couldn't go to the vet to watch.
Sorry to hear about your cat, Dotsie.
I've lived for over 2000 years, and not all of them were good ones. I've made many mistakes. And it's about time I did something about that.
-The Twelfth Doctor, Doctor Who: Deep Breath