I submitted a manuscript

yesterday. No, I submitted the first three chapters yesterday. I hope I followed all the other instructions carefully. 
This scares me but I am trying again. I am not sure why I am doing it. Am I a masochist? 
I put the book aside for over a year. I put it aside because I submitted it elsewhere, to several "elsewheres" in fact, and received no response. 
"You need to think about this Cat," I told myself. I know that people can submit books "umpteen" times and more before they succeed. I know I may not succeed this time. 
Putting the book aside was not "giving up". It was wondering whether it was good enough . "Good enough" means so good that someone else would think it worthy of a wider audience.
I am not holding my breath. 
First of all it is, in one sense, an "old-fashioned" adventure story. You know the sort of thing I mean. The children are on their own (for part of it) and things happen. It is based on a true story so it is dangerous and deaths occur.
The second thing is that there is a child with a disability in the story. She is not the main character. I know putting such a character into a story is tricky. There are too many books where such characters do amazing things or have miraculous recoveries or have genius ratings on IQ tests. It doesn't happen here. She's intelligent but not a genius - and she also works hard to get her results. All the same I wonder if reading the first three chapters makes the adult reader wonder if she is one of "those" characters. There is nothing I can do about that. Children read it with different eyes. 
The third thing is that the book is not set in the twenty-first century but in the middle of the twentieth century. There is good reason for that. It allows distant communication to be poor. The book is set in two countries - half a world apart. Travel to and from then was not nearly as common as it is now. Letters were much more common than phone calls. But, doing that means it is almost historical fiction in the eyes of some people. They expect to see mobile phones and computers and more in any book. 
Of course other people may find many other things wrong with the book. It would have been good to have someone cast a professional eye over it and say "That is wrong. Cut this out. Put more in there. Take that scene away. Why did you do that? This is superfluous."
I'd like someone to professionally read it.
So, I am trying again. When I went back to my characters with, hopefully, a fresh eye I thought, "They are nice kids. I still like them the way I did when I wrote about them. They deserve to be introduced to the world."
After all, they told me what to write. I don't want to let them down.