It's not that i can't stomach it, but it is hard to watch such a beautiful creature go through such agony.
Once again I am going to say this and I hope it connects with at least SOMEBODY. [>:]
As long as the arrow was well placed, the animal is NOT in agony. It's not even in pain. For one, it is in shock from blood loss. For another, they don't have the same pain receptors humans do.
What it is, it's confused that it can't get up and run. And if you're standing there watching it where it can see you, it's plain terrified and desperately trying to get up and escape with it's last ounce of strength. Repeat: It's TERROR, not agony, that you're watching!! And you are causing it by being a complete doofus.
Back off, LEAVE IT ALONE and don't freakin' watch it. It saves your feelings and it lets the animal calm down, fade away into unconsciousness and die in peace.