Always ..... it broke my heart when my dog stayed overnight at the vets and we had a call at almost midnight to say that he had gone, not expected either. We had to pts the last of that era of dogs just a few weeks ago and we were all there saying goodbye to Maisie who became very poorly - if we put her through surgery which more than likely wouldn't have worked as she wasn't strong enough, it would have been for our benefit, not hers .....
I think that the experience that sticks in my mind though was when my my old friend Sydney died. I had always wanted a horse, and despite being disabled I finally got one at the age of 50. He was an elderly gentleman, who in his day had been there, done that and had got the tee-shirt, like me he too had arthritis and we both took a bit of getting going in a morning! But he wasn't unwell and it was good for him to keep moving in a safe ploddy sort of way, (not always, depending ho was on him!) and good for me too. I could no longer 'ride' per se, but could sit correctly and balance, but wasn't able to use my legs, but Sydney and I had marvelous voice activated rides, and he would stand at the mounting block for 20 minutes if he had to for me to get on and off, a 2 or 3 man job! Sadly, one evening when I went to give him his dinner, he was very lame, arranged for the vet to see him first thing the following morning, but when we got there early he was already down. He had cast himself up against a fence facing the wrong way to get him up without digging the fence out and there were no signs of him even trying to get up at all - it was almost as though the had gone down in that spot deliberately, knowing ..... I then had to call his 'Mum' who had loaned him to me, and she took an hour and a half to get to us as didn't live nearby - that time was spent giving him his favourites, pears apples, carrots and Murray Mints and giving him scratches in his best places, cuddles on the floor, and all of his favourite people around him. The vet actually said she had never seen anything like it! There were 9 of us there saying goodbye to the most special boy to us all - he helped me when disabled, his other Mum had had him since he was young, he taught my young friend to ride (who is now a work rider for Andrew Balding and hoping to take his jockey licence soon) he gave my daughters a different ride as he knew they could cope with him if he misbehaved (NEVER EVER with me!) He went to sleep peacefully and gently with us all and despite it being 'horrible' it really was a beautiful way for him and us and couldn't have been any better at all ....
You must always be there, if you can ....