Euthanasia: the act or practice of killing or permitting the death of hopelessly sick or injured individuals (as persons or domestic animals) in a relatively painless way for reasons of mercy.
It's never an easy decision, but it's sometimes the right one. Most would agree that it's selfish of us to prolong an animal's physical suffering when it has a terminal illness or painful injuries that will never heal. Often overlooked are animals with mental illness. An animal who suffers from dangerous compulsive behaviors, debilitating fear, and other invisible conditions that diminish their quality of life are no less worthy of mercy and peace. The afflictions may not be visible so it's harder to justify euthanasia, more often framed as a punishment for something that the animal couldn't control, when in reality the punishment is to sentence them to a tightly managed life full of stress, fear, and danger to themselves and others. When "no kill" becomes synonymous with "no quality of life," we've put our own selfish feelings ahead of the best interest of the animal we are so desperate to save.
Attempting to hide an animal's physical suffering from the person charged with helping it is undeniably cruel to the animal. Making excuses when there are clear signs that the animal is suffering from a nonphysical illness is equally cruel. One of the greatest gifts we can give with our stewardship over other living creatures is freedom from suffering. With our power over animals comes the great responsibility of trying our best to treat them well, always striving for the ends to justify the means. The even bigger responsibility is knowing when the animal is deteriorating physically, mentally, or both and the kindest thing to do is help them leave their suffering behind knowing you gave your best shot.
Bless the brave souls who shoulder this responsibility, pushing on through the tough judgment calls, broken hearts, and criticism to step up and save who they can and give peace to those they can't.