That's the worst part of having any pet
The best dog I ever had was a Westie. Loved that girl! She lived until about 14 yrs old but by then, her eyesight was gone, her hearing was going and she started having seizures that kept getting progressively worse. It was so hard to lose her.
Yes, we can get attached to our pet's, and they are missed when they get old and pass. I took in my dad's old dog that was a mini Schnauzer when he passed, because Richie was old enough that no one else wanted him. My dad was his second master and had taken him in when his first master died. Anyway's, Richie lived to be 18, before thing's started breaking down on him so bad. He had a stroke, and had gone blind also so he could no longer find his bowls of food and water.