Why is it that most books that are Classics make me feel bad

Why is it that most books that are seen by the world as Classics make me feel like shit?

It's like they are saying if a book is funny or makes you happy in any way, it is a bad book. I am not good at learning from things that make me feel even more depressed. I can't think about the way someone’s writing changed things ect. if the story makes me feel so depressed. I know that books can be funny and well written even game changing ect. like Jane Austen, William Shakespeare, and Henry fielding. So why is it that 99% of "the Classics" are things I can't read without have a severe depressive episode from it?