It's painful to recall. My male cat, "Fluff," who was my loving buddy for 10 years, became lethargic and thin. He was not interested in eating and I took him in to the Vet.
The Dr. decided to keep him overnight for tests and xrays, etc. I never expected the call the next day that explained Fluff had congestive heart failure. The Vet assistant was very kind and gentle in telling me that the Dr. suggested euthanasia to avoid slow and painful death.
I was shocked and sad (crying) but knew I surely didn't want him to suffer.
The Vet I went to has their own pet cemetery (at no cost)......which I feel is a comforting benefit. They even sent me a sympathy card for the loss of my beloved pet. I think that is a special gesture and I appreciated it.
I grieved for a long time and I still miss him. After a few months, I adopted a kitten who reminded me a lot of Fluff. I poured my love into him ("Tommy").....and he's a joy, but of course, no pet is ever "replaced". They are as unique as humans.............