Part of this is you feel guilty for your kitty's death bc you weren't there. People and cats often don't want their loved ones to see them pass. My Grandparents were not leaving my Dad's deathbed so he asked for a glass of water. When they went to go find it , he passed. My Grandma passed like at 3 in the morning when she would have privacy. I didn't know until I woke up to give her some pain medicine. I remember feeling really guilty for her death as she got pneumonia after falling while I was in the bathroom putting my hair up. I felt responsible. For whatever reason those feelings are natural but not the truth. She was elderly and had lung cancer. Your kitty had a heart problem. No person or animal lives forever. I now feel my Grandma with me often. I believe your kitty is still close to you. We have all done things we are not proud of. You are a brave person to admit it. You have grown as a person. Show yourself the same warmth and compassion you have for kitties and turtles. I'm like you, I think. I pick up worms in the rain and put them back in the grass and gardens so they won't drown in the rain. I have a dog who is a cat lover and we have 3 cats. My animals are the sweetest things. My one cat doesn't greet me or rub against me when he comes home, he rubs against the dog and greets her. I always find them together.