How Can I Overcome This Sense Of Loss & Guilt?

I had to have my cat Preston put to sleep Monday. I buried her and then had to get on a plane to go on a business trip to Washington, D.C. I'm still on that trip, but just going through the motions. She was my friend for 11 years. Our time together started when I was on another business trip in Dallas. I was staying at a hotel called the Preston Suites for a couple of months working on a project. There was this little stray cat that I started feeding and eventually became so attached that I knew I had to take her home. I decided that I would buy her a plane ticket and for the last few days before I was going to leave for home, I kept her in my room with the Do Not Disturb sign on the door so the maid wouldn't let her out. So I took her to the vet in Dallas, went and bought a pet carrier and we both flew home to Kansas City. She didn't have a tail so I thought someone had been mean to her as a kitten but the vet in Dallas told me she was a nationality Bobtail.

She was an awesome and loving cat. I felt guilty over the years leaving her at home while I traveled on business, but my mom lives a few miles away from me so when I was gone, she would make sure Preston had food, water and love. Preston would always be at the top of the stairs to greet me when I got back.

Four months ago I moved to a new house with my girlfriend. About a month after I moved I noticed Preston started throwing up a yellow substance. I pretty much ignored it for a couple of weeks just thinking it would go away. It didn't and she started losing weight. I took her to the vet and they did blood work, x-rays and a sonogram. She had elevated liver enzymes. The doctor said he could do exploratory surgery, but I thought that at her age maybe that wasn't a good idea. They gave me anti-biotics and Prednisone. I actually thought Preston was turning the corner and going to be fine because the vomiting had stopped. Sunday night I went to see her and she was laying on the floor not moving. We rushed to the emergency vet and they told us her blood sugar was so low it didn't even register on the test and that her weight was now 3 lbs. Just some skin and bones eventhough for the past month I had fed her canned food twice a day and she always had two types of dry food available.

The emergency vet said she wouldn't blame me if I had Preston put to sleep that night, but I just couldn't. I wanted to wait to see what the specialist had to say the next morning. He said that we had tried antibiotics, Prednisone and additional nutrition and that her liver was just failing. I fell apart. Basically I held and patted her while she was being euthanized and even up until the very end she was trying to give me love. It was the hardest thing I've ever had to do.

I'm devastated and am not functioning very well. I know Preston was at least 12 years old I(when we got home I took her to get her spayed, but when they shaved her belly she already had a scar there) but I was not ready for her to go yet. I am racked by these feelings of guilt -- why didn't I take her for regular checkups, why didn't I ever have her teeth cleaned, did moving trigger some kind of stress that started this whole disease process, did I give up too soon, why didn't have have the exploratory surgery done a month before, why did I wait for a couple of weeks before taking her to the vet? All the times she wanted love while I was working on my computer and she would walk across the keyboard and I would just pat her head and set her down. I miss her so much. It was her and me for many years and then I got engaged to a girl with a dog and then we got another dog and Preston didn't come out of her room anymore because she was afraid.

I just feel like I failed her. I would give anything to have my little friend back and I'm hoping that eventually the pain will go away.