I've been writing since I could hold a pen. So there are plenty of doozies out there--embarrassing early works, that is. Poems I wrote to ex-boyfriends. Poems I wrote to friends. Poems I wrote in the backs of yearbooks, even! (No "Have a nice summer" messages from me.)
But really, the doozies didn't stop there.
It took a long time to sell a book. Seven and a half years of full-time effort. And that was after I'd gotten a master's in English. Every mistake you can make, I made it. And that's regarding the work itself, not just the five-page queries or the fancy envelopes for unsolicited manuscripts (because, yeah, when I first started, I was submitted via the snail mail).
Looking back, most of my manuscript mistakes followed similar patterns:
This was probably my biggest problem. I'd spent most of my life reading quiet books. Literary books. College reading lists brought me more of the same. I love getting in the head of a main character. In so many ways, I think we learn so much about empathy from reading. But here's the thing: Each main character needs to change. Needs a character arc. That change is facilitated by the events of the book. Without some interesting events (a tight plot), the character arc often winds up being weak as well.
Weak plot = weak character arc = weak book.
Too Much Internalization
This springs off the previous point, but my earliest books were incredibly internal. Lots and lots and lots of thoughts. And feelings. And more thoughts. And long paragraphs. And not enough happening.
Too Much Attention to Literary-Style Phrasings
Some of this goes back to my literary reading. I was always interested in description. In how a story was told, rather than that events that happened to a character. But I think too many literary bells and whistles can distance your reader from your main character. Keep them from connecting.
Clearly, the best advice I can give any writer is to really work on plot. I've become a junkie for technical books about plot structure. So often, if you've got a tight plot, character development will naturally follow. And, of course, you can insert a few literary devices to help tell the story.
Yes, more and more, I do believe it's all about plot.