Death
It's the ultimate white elephant in the room. I think people only remain sane by never thinking that they'll eventually be dead. Because, really, it's a very unsettling thing to consider that you'll one day no longer be a part of everything you've ever known. And there's no saying how it will happen. In traffic tomorrow morning, an unexpected heartattack, or getting stabbed by some random crazy person when you're walking down the street. Most people who die unexpectedly didn't wake up that day knowing their life is over. I'm scared. Hug me.