“I hate writing, I love having written.” - Dorothy Parker, and also you
Sitting in front of a blank page and feeling nothing.

...Except panic and low-key despair.
Legitimately not being sure if what you've written came from you or was something you'd read before.

"This is too good. Did I really do this?"
CW
Sharing your writing with other people.

...And, then, the torture of having to watch people AS they read your work.

"Is that a smile of approval? Or do they grin to keep from weeping?"
ABC

19 Way Too Real Nightmares All Writers Have