I have had two dear friends lose feline companions recently - one to an automobile and another to cancer. My heart hurts for them both. When you have an animal companion in your life for a period of time, you become quite attached to him or her and many people consider their animals a part of their family and most of those people would tell you that they love their pets.
So when your pet dies, it hurts a lot. A big piece of your life is gone.
Both of our kittums are getting up in age and I worry about their health. Fortunately, the vet says they are both quite healthy for their age (both are around 12 years old). I hope they are around for many more years.