One more edit may be an edit too far

I finally have my almost finished manuscript, but the editing stage has gone on for so long I am starting to question why I even bothered to write my book.  is it really any good?  Will anybody want to read it?  And, if I start sending it out to publishers and agents, will it come back to me so fast it's like there was a boomerang attached?

All sorts of worries go through my head and the thought of them makes me doubt my work and then I start to think - do I need to change what I have written?  Should I keep this bit? 

One of the best pieces of advice I read came from a very successful author who said that there is a danger of making changes to your manuscript not because they are better, but because they are different.  I have that on a post-it note and every time I consider making changes I stop and ask myself 'is this going to make my book better?'  If the answer is no, then I keep it as it is.