On the 24th I had to put my dog down. He was 15 years old. His birthday was in a couple months. This was probably the hardest decision of my life. He kept falling down and tilting his head to one side. The vet said he believed he had a brain tumour which was screwing up his balance and will only get worse with time. Said it didn't look like an ear infection either. He had about 3 previous episodes where he would keep falling down and had a hard time getting up, I would pick him up and he would be fine after a couple minutes but this day he was in this state all day so I figured there I had no other choice. I felt very guilty afterwards. Guilty that I made this decision and guilty that I couldn't stay when they gave him the lethal dose that put him to sleep. I stayed to the point where he was sedated and was petting him the whole time but I didn't have it in me to watch him die. And as OP said, What if we waited? What if we got more tests done and it was something else? The only treatment available for a brain tumour was surgery in Vancouver, $5000-$6000 which I could not afford, and no way they would do it over the holidays anyhow. I'm still having a hard time trying to cope with this loss. He was my best friend, always by my side. Every time I get home now I look to the couch he would always be sitting on waiting for me. I know it was the right decision to do but I still feel very bad that it had to be done. Man I'm going to miss him. I know he lived a full life so I'm trying to not feel too bad.
All the same feelings jcairns expressed, I felt as well. I want to own another pet down the line but not for awhile I think. I had this dog since I was 14.