The inevitability of death, illness, sadness and anything negative which is a core part of life for everyone. I just find it hard to accept it and be okay with it.
I'm supposed to cherish life, yet if someone offered me a bucket with 10 apples, 8 of which were tasty and 2 of which were rotten, and I had to eat all of them, I'd rather not eat any y'know? I'd consider that a terrible deal. Yet I'm supposed to be okay with a similar arrangement when it comes to life...