Euthanasia is killing a dog, we can all make it sound pretty by saying that it is putting the to sleep, however, the fact of the matter is they are being given a lethal injection. Many beautiful, healthy dogs are killed due to humans being idiots. There are times when dogs are PTS due to illness, or injury, and although this may be the "right" decision it is still awful.
Whenever I make the decision to put a dog to sleep, I stay with them, until the very end, as I feel I owe them this much. Even if they are aggressive they deserve someone to be with them as they take their last breath. Some dogs go peacefully, however, others know, they can sense it, and some fight it with all they have.
I have been at the vets where it has taken two or three of us holding the dog down to even find the vein. Thankfully the vets are experienced, and this process can be done quickly, but with a dog that doesn't want to go, it is an awful few minutes. The dog will thrash, and scream, knowing they are about to die.
Often dogs do not just "go to sleep" some have spasms, and take more of the lovely red liquid, and others will keep fighting until they can take no more. Once they have finally gone, my dogs have the privilege of being dealt with "nicely" However, many don't get such a luxury and end up stacked, in binbags waiting to be collected.
What happens to your dog next... Are they cremated? dumped like rubbish? made into animal feed? You will never know, and too be honest do you actually care. Your dog was just another thing that you got bored of, and threw away. If you don't want your dog anymore, have the balls to stay with it until its last breath... you may think twice about giving up on the next one.