One of the things that helped me the most on the way to finding a publisher was learning to love criticism. Not just accepting being told what doesn't work but really looking for it.
Criticism is hard to hear because it's usually given as a negative statement and nothing more. In life if you're pleased with something the last thing you want to hear is someone telling you why it's bad. But if you're working on a book, the critic may have discovered something about your work that's fallen short. It would then be up to you to explore what they said and potentially improve the story. So, I see it as an opportunity.
I'm grateful for all the criticism that I received during the writing process. It made 'Camouflage' a more thrilling story.