My cat died nine months ago and I still grieve over him. Is this normal?

I had him ever since he was a kitten, and he was eleven years old when he passed away. His death was tragic. He had a nasal tumor that I was going to have surgically removed. When the vet put the breathing tube in his throat he stopped breathing and they lost him. He had undergone many surgeries before this, so it was a total shock to me when it happened. I was so upset I cried all night and couldn't sleep. I still cry about him probably once a week or so. I did end up getting another cat and I love her too, but I still think of Sherman every day. I miss him so badly and I've never gotten over his loss. Is this normal? I've lost other pets in the past and it never hurt like this. Sherman was always by my side through some really hard times, like my divorce, and now he's gone. Every time I look at pictures of him, my heart aches because I want to hold him again. The last few weeks of his life he was so sick. I hand fed him and did everything I could to save him.