I read once, not sure if I'm remembering it correctly, that Agatha Christie was not sure of her own writing.
I know I am not writing the Great American Novel (if there is such a thing), but I do so enjoy the writing. Well, I enjoy the story. I write to find out what happens. If I were not a writer and heard such a comment, I'd think the person was bonkers.... But now, I see that the story comes to me (usually with a beginning and an ending), but with nothing in between - and I desperately want to see how the hero / heroine survives, if at all. I want to know if the villain wins. I want to see what their friends do. Are they steadfast and true? Are they wishy-washy? Are they cowards or fakes?
That's the best part of writing.
The editing, as I've said before, can just destroy me - And the joy of the book. I hope I can survive the publishing process and still be able to write afterwards.
Deflating joy can be traumatic. And I think it is hard to get the joy back.
BUT - I will persist.
I know that's one of the reasons that I started 'Nothing But Blue Skies' in the midst of editing 'My Sword Sings.' It gives me the joy of writing, while I wallow in the quagmire of editing.
Good luck to you!