It is hard to deal with death sometimes. I go through a period of shock myself, and then get hit hard with a depression afterwords.

I guess you were very close to that cat, I had a friend who was like that with his cats. He grew up with them and then after high school one of them died. It was like he lost a brother or sister. I had a family dog that had to be put to sleep when I was a young teenager. I was really sad afterwords.

After that I lost my grandfather and was even sadder.

Best thing you can do is try to remember the good times you had with the deceased. Keep them alive in your heart.