We lost one early to kidney disease. One week he just started acting off, not eating normal, even found him hiding in places (which is never a good sign). Started losing weight visibly, so we got him in to the vet and the blood work comes back. We took him home for one last night together with the other cats before taking him back to let him go. Still rough to think about. We've lost a few others mainly to old age, which is still hard, but to cut a great companion's life in half out of the blue...