I hate losing pets; it is the only downside to owning pets.
At age 55 and have had animals almost all my life, it is always with you... sooner or later..
I lost 3 cats over the space of 1 1/2 years. One threw a blood clot @ 10:30 pm one night: I thought the poor animal was yowling at an interloper and when I looked out he was lying on the terrace, appearing like he was just watching the night. I am glad I went to the door: I had cut a hole in it for a future cat door and he tried to come in but collapsed. The damn clot had lodged in the arteries to his hind legs. I never drove so fast to the local emergency clinic which was a good 4 miles. I was lucky: all the lights were with me and I didn't run into any cops. The clinic said they could save him, BUT the chances are he would throw another one and since the cat was in and out I didnt' want to chance him dropping away from the house, suffering wihtout any aid, and dying alone so I made the decision. I took the next day off from work as I didnt' go to bed til 2 am.
The next cat died of cancer. Was the size of a bloody grapefruit and was impeding his ability to breath: Cancer is a bastard.
Last one was Trinket who died of complications from old age. She just couldn't keep any weight on her old bones.. Shortest lines for one of the best cats I ever had. I did not go in to work that day either.
I currently have a 4 year old colour point lynx (all the above animals were rescues) and a mutt whom I got from a flea market: fleas and all. Mutt is 11.