Yes, Rocky, it is hard but it's so much better than letting it suffer. When I was around 10 years old, a stray dog was run over by a car and smashed bad. I couldn't stand to wait for it to die and be out of it's misery. I grabbed it up and carried it to our nearby creek and held it under to drown. It may have already been dead when I got to the creek but I wanted to be sure.
It's a pity that humans aren't treated as humanely. I've always thought that death is not as bad as irreprable pain.
There is a beautiful dog that lives on Dave Buck road (above the house) that comes to my house every time it gets out , through all kinds of weather, which is often and stays with me 2 or 3 days at a time, before they come after it. Often it wakes me up barking to get in. It's a maltese, young and with a wonderful disposition.