Years ago we went to a recue centre to get a dog. We ended up going home with a ten year old called Candy! She was overweight and a bit ill, so we put her on a diet and sorted her out. She was a good friend, really placid. She was so lacking in confidence that she didn't bark for the first few months.
We had her for a couple of years, and then she stood up one day and just fell over with a burst appendix. A couple of weeks after her op, the results came back. Turns out she was riddled with cancer too. No amount of medical attention could cure her. We took her to our local vets and had her put down. It was hard enough as it was, but she was sitting up when the injection went in, and I had to catch her on the way down and let her fall gently. Broke my heart.
I love dogs, I'd love to own another one, but the time when they go is a lot to take. I'll own another rescue dog at some point though, I prefer to give abandoned animals a second chance. They've already been dumped once, and they have feelings too.