It's the walls.
Often a client asks, as you gather around the table with its dog or cat lying still and quiet upon it, but no longer in pain and despair, thanks to your needle and skill......"Doc, I don't know how you do this...." And their voice hangs in the air, dripping a bit on your shoulder and bowed head.....
You tell them that this is one of the most important things you can do, for when all else is done, you can grant a quiet exit for a dear friend, so that is what you do. And they thank you through their tears and you hug and then they leave so that you can wrap up a limp body in plastic and place it carefully in a freezer. And the pain settles in there, and you promise yourself that it will be ok, and it is not, and so you build another wall.
That spot inside your right cheek, the one you chew on when you really need to rip some asshole's head off and you cannot, and you watch them take the abused neglected animal away to where you cannot force them to let you help, and you know they will let it rot, and you say to yourself....forget it. It's not your problem anymore. Get on with things.
And the pain settle in there, and you build another wall.
Soon enough you are so changed that you cannot see yourself without walls, and you cannot see outside the walls, and those you love cannot see you within.
And then somebody puts this silly thing up on your feed, and they force you to watch it even though you fear it, and it works. It finds a way through all the walls, and it feels for and then hits that place deep in your heart, and you feel the walls fall away leaving you completely exposed and defenseless. Perhaps the tears flow...
You wonder for a moment why this one gets to you, and then in the mirror you see..... This is why you do this thing, for them and despite what it does to your self. But you have to drop the walls before you can even remember why. It takes a silly thing like this to drop the walls.
That bit is the sad bit.