some older!pet whump thoughts™:
Pet knows it’s no longer useful, what with the way its endurance and pain tolerance are lowering, how its skin is deeply lined and weathered, and how its once strong body is now battered and weary and aged and ugly. It has seen how Master now glares at it with barely-hidden disgust, how often Master has kicked it and it couldn’t get back up afterwards. It knows Master wants a younger, more useful pet. (Really, that’s the most terrifying part. How long will it take for Pet’s usefulness to be finally wrung out of it? How much more time until it’s tossed aside like the overused rag that it is?) And even if it wanted to, it can’t hold any contempt for Master. (Whoever that newer pet was, it would be better than Pet in so many ways. Master deserves good pets.)
It just didn’t know what would become of it once it had outlived its usefulness. Would Master kill it? No, no, an old bag of bones like Pet didn’t deserve that effort or mercy. Most likely, it would just be… discarded. Maybe in some back alley in the worst parts of town (where anyone could find it and beat it worse than Master ever had or use it in other ways until it’s a quivering, bleeding mess—) or in some field (where no one would ever find it). Maybe Pet didn’t even deserve that. Maybe it would just be cast out the door, and it would be forced to attempt to fend for itself and starve to death alone.
And Pet couldn’t even do anything about this. All it could do was wait. Stew in its own miserable, spiraling thoughts. Stress itself out by being utterly, disgustingly helpless and fry its stupid little dog brain over what could possibly happen and how it could die. Wait. Wait. Wait.