I had a 3-year-old cat who died in June this year. I had rescued her from a pound in August 2005. A few months later, she was diagnosed with a fatal, incurable disease called
FIP. Not many cats survive FIP (the mortality rate is above 95%, less than 1 in 20) but I wasn't going to give up on her. Numerous visits to vets and specialists resulted in her eye being removed in November 2005. A mere seven or eight months later, she showed obvious signs of succumbing to the disease (yellowed ears, extremely difficulty walking, no appetite, particularly long periods in out of view places, etc.). I had her euthanized on June 15, 2006, shortly after 5pm, because she had obviously lost the fight (and the vets she saw shortly before that day agreed wholeheartedly). I could barely stand to sign the authorization papers, and spent a few minutes crying in the car before I drove away.
I only had her for ten months. But until near the end, she followed me around and sat on my lap and purred as I pet her. She groomed my other cat. She made biscuits on my leg frequently. I played with her. She rarely did anything bad at all (from a human's perspective, of course). I didn't have her long, but boy do I miss her. The fond memories I have of what a sweet kitty she was. I've never met a sweeter cat. And I strive to make my current kitty as comfortable and happy as possible. I value every moment she spends with me. Even if she's not as social towards me.
I also have memories of two dogs I had who died in their old age. Jimmy succumbed to a parasite at the age of 17. He'd lived with me and my family for 16 years, and I am not kidding when I tell you my brother and I, normally fairly stolid guys, walked around crying for a while. Jimmy was our childhood dog, and we both remember playing fetch with him and petting through the years.
The other dog, Fling, was 16 when he died. I taught him how to catch discs in the air and he was a wonderful australian shepherd. He was fiercely loyal to my mom; once, he bit a guy in the crotch because he yelled in her direction, even though Fling knew him. He followed my mom literally everywhere. He was awesome.
I totally agree with remembering the best times. Make the most of your pet's life. Make the most of
your life too!