Book-related things that give me anxiety:
1) Finishing a book and not knowing what I should read next, because my TBR is overwhelming.
2) That I can never possibly read all of the books that I own in my lifetime, even if I never get another book ever again.
3) That I can't support everyone I know who writes books by buying their books.
4) What if something untimely happens and the book I'm currently reading is my last?
Just to name a few.