Nancy Peacock has done well as a novel writer, and her path has been a challenging one. Speaking of her mindset about ten years ago, she writes,

At the time, writing and publishing another book was the last thing on my mind. Although, even as I say it, that feels like a bit of a lie. I think publishing is always on a writer’s mind; I also think we have to forget about it. We have to write without feeding any fear regarding the future of a book, how we’re going to publish, how we’re going to reach an audience, and how the book will be received.

She describes how she soured on traditional publishing, chose to self-publish her third novel with professional help, and the key that turned her back to traditional publishing.

http://www.writersdigest.com/editor-blogs/guide-to-literary-agents/indie-author-landed-traditional-book-deal

Peacock doesn’t talk about her experience with queries, but whatever mistakes she may have made, I’m sure she didn’t make any of the ones agent Steve Laube lists in this post on odd queries he’s received.  Here’s one of them.

An email proposal with a cover note that reads, “I am sure you get a lot of proposals, but this one is worth your time to read.”
But the author claims they looked at what we agents want and then sent us something we specifically say we do not represent. Then says they followed our guidelines for submission but didn’t follow one of them. And then claims the Holy Spirit told them to write it and gave them the words. They must not have read what I wrote a while back “God Gave Me This Blog Post.”