Sorry, Thrills. That really really sucks, bro.
To answer your question.... yeah, seems like we all have a story.
Before we had kids, my wife and I adopted a kitten and it wouldn't shut the fuck up, so they told us to get a companion. We had every intention of getting another kitten or young cat.... but when we went to THS, we fell in love with this old (13 yrs), obese, crooked-tailed, black cat. It reeked of urine because it was too fat to clean itself (about 25 lbs)..... but we adopted it. It wasn't long before he was pissing 79 times a day (usually missing the box) and the vet told us that he was diabetic. So, we gave him 2 shots of insulin a day every single day for the next 7 years. Once that started, he got much healthier, lost some weight, cleaned up, played with his little buddy and was generally as adorable as a cat could be. Then, when he was 20, he started to slow down... had trouble with his hind legs, got tired real fast. We took him to the vet and they ran a bunch of tests ($750 - bastards), but couldn't figure out what was wrong, so we took him home. Within 2 days, he got much worse.... back to the vet. This time, a much more experienced doc felt him for about 3 seconds and told us there was a tumor the size of a baseball in his abdomen. They said it wasn't sure how long he could go... maybe a month, maybe 6. The next day, he got so much worse (I had to carry him to the litter box, he couldn't even walk), that we decided he had to be put down. So, we spent an hour saying goodbye... taking pictures... crying a lot.... and then walked him over to the vet and had him put down. We both stayed in the room while they did it.... I don't advise anyone does that... I sure won't the next time. It was awful.
The next week was so horrible. The pain of the loss and the whole experience was unbelievable. I've never cried so much in my life. Orson was the best cat ever.
Sorry for the long story.