Testing the limits

I finally came up with an idea for my "First Book". So I have written stories before. I have at least two great manuscript, in French, but it's not the first time that I have written a story. I have a prologue written and a nice two liner of a first chapter. I don't really know where the story is going, but it doen't make me too nervous. If memory serves me well, I never know where the story is going. When I do,I juust screw it up - perfect example of this, my Clark and Chloe story on Fanfiction "Worth the Wait" - I had plan it to be 10 chapters where Clark and Chloe reconnect and realize they were idiots for not trying to make things work between them eons ago, instead, I completed an posted chapter 10 5 months ago, have rewritten chapter 11 - 7 TIMES!! and still no end in site. I just don't know how to plan and follow thru a predetermined story line. This might be a hurdle for me as a writer. So I hope myself all the luck in to the world because ..I am going to need it