We had our terrier for 14 years. On Saturday, July 20th, he passed away at home, after we were adamant about taking him home from the vet following a tough day of "treatment".
A bit of backstory: He had breathing problems due to a heart condition. Fluid built up in his lungs because of it which was when we took him to the vet on Saturday morning. We took him to either a) see if we could get something to ease the stress he was in (as we had also done on Thursday to help remove the fluid in his lungs. That visit went well but we had a different vet attend to us then.) The other option was b) If it was necessary, we would help him have a peaceful pass over if there was no hope of recovery, as it did seem his general breathing problem was worsening. However, the vet who attended to us on Saturday treated us very oddly; dismissing our feelings, and taking all our questions and suggestions as if we were doubting his expertise.
Though my mother was very hesitant, we eventually agreed to leave our boy to be "monitored" by the vet throughout the day. (She was hesitant, because we know our dog very well, and know how he reacts to being confined. He panics and instead of staying put he just goes around in circles, banging his head everywhere -- his vision had been impaired due to old age--searching for a way out. Looking at the vet's facilities, we knew he would not be comfortable.) About 2 hours after we left we got a call from the vet who seemed panicked as our dog's breathing issue had "escalated" (likely exactly what we had warned them against had occured. Our dog more than likely panicked when he got up and realized he was in a tight, unfamiliar space, without us around), the vet told us they had decided to "revive his system." We rushed down to the vet and our dog looked so bad and uncomfortable. They hooked him up to drips saying that he had lost a lot of fluid in the time we left him there. There were tissues with blood everywhere and he had a line of blood on his front, left hind. Even the way he was laying looked abnormal. The vet insisted we keep him there for the rest of the day. We returned to the vet at 7pm, I took one look at him and knew it wasn't good. The vet kept telling us that compared to the dog's condition when he had his episode at their office earlier that day to what he was at 7pm that he was doing better, but we had never seen him look so bad. The vet still made an attempt to have us leave the dog alone during the night, knowing that there would be no-one there to monitor him. But my mother said no, she's taking him home and if needs be, we would bring him back the next morning. Two hours from when we brought him home, his little heart beat for the last time and he took his final breath.
I was relieved then, to finally see him at peace after such a tough day, and knowing he was living with a condition that brought him discomfort. I was also comforted to know that he didn't pass alone in a strange place (i.e the vet's office). We buried him on Sunday. I made him a little shrine with a few photos, his dog collar and some toys and still felt comforted then that he was no longer suffering. However after midday on Sunday, that's when grief struck. It was a beautiful day, and while I was sitting in my living room I could hear a bird chirping loudly outside. Where I live, hearing birds is a natural fabric of life, but this bird's chirping stood out. The peace it brought as I sat there, conjured flashbacks of our dog's life. I could see him, when he was younger, sauntering along the deadend road back to our house. I could see him as a pup, eager to play fetch, mischievously rangling slippers left out of closets, clothes that failed to make it into the clothes hamper and books from the bottom of the bookshelf. I could not stop crying. I woke up this morning, and when I was finally left home alone-- as I work from home-- his absence brought and left tears in my eyes for the entire day. I got absoluely no work done. I couldn't. I realized today, that since I started working from home in January, I spent lots of time with him and our other dog, but obviously he, being quite old, required lots of personal attention and care, that I was glad to provide. So everytime I walked out of a room today and didn't see him in his "spot", it stung.
I will say that I do feel happy that he lived a wonderful, long life, and was deeply loved. He is already greatly missed and I hope, wherever his spirit is, it is happy and at peace.
Although a few friends know of his passing, I just have not been able to express all this to anyone and felt it was important to let it out. Thank you for reading if you have. If you have lost a pet, I hope the memories of you guys' time together bring you much comfort. If you currently have a pet, I hope you two share all the snuggles, love and loyalty that is so potently present in the relationship between a pet and their human companion.

All the best everyone.