PS to add to JJ's comments; I did edit it myself to a point, but then knew that it was essential to hire an editor, and graphic art expert too, as we got closer to publishing. I was very fortunate to find an excellent editor at a reasonable rate. She didn't know me, but would phone me and ask me if this particular section was supposed to be that way (ie, was this 'my voice', or a mistake). She gave excellent advice, most of which I took and incorporated into the book, some of which we both decided against because it would have changed my voice too much. Hiring her was the best gift I gave myself, and I wouldn't hesitate to do it again.

Same with the graphic artist, who was the one responsible for putting all of that edited-and-perfected work into an eye-pleasing format...we actually had to go back and reword many paragraphs all over again, once we saw it in its final format, because of orphaned words and/or sentences. He's also the guy who designed my cover. He read my book so many times, and called me to discuss parts of it, not so much for editing purposes, but to get to know ME...when he came up with the design cover, I was awed by how well he "got" me and the essence of my book.

The two together (editor and graphic artist) cost me a lot of money, most of which I'll never recoup because I printed more books than I could sell - that's another story if you're interested - I only wanted to print 1000, but was sort of strong-armed into printing 1500 - I've sold/given away close to 1000, but will probably never get rid of the other 500. Another example of the consequentces of not listening to my own instincts.

In the end, you do have to follow your instincts, but you can end up also paying a price for not following the advice of the professionals. For me, insisting that the book be my story in my own voice rather than following the formula that mainstream publishers demand meant the difference between being accepted by a recognized publisher and having to self-publish. But if I had chosen the other route (which at the time I equated to selling my soul), it would not have been my book or story anyway by the time everyone else had it changed to suit their tastes, so what would I have gained?