Welcome to Gaia! ::

I've had that same problem with two stories I've been working on since I was about ten too. The best advice I can give from personal experiance is to pick one and think about it when ever you have time to think. Think of differant possabilities, outcomes, and characters or situations that could help the original story line keep going smoothly even if that means adding in a sub-plot or putting another story on hold. Once you get the feel for how the begining, middle, end and everything in between should go then just start writing, jotting notes down, crossing out notes that don't work, and always keep an open mind but never forget what your writing about. Also, write to please yourself. If your happy with your work other people will love it to and if they don't, thats their own fault. *Good Luck*

I agree with Lunar to some extent, sorry lol. One thing I find that helps some is to just put it aside for a while, but not completely forgetting about it. Since you don't have an editor/publisher I'm assuming, you don't have a deadline so it's not like you have to rush anything. Just put away the actual writing part for a while and take the ideas/story line, etc. around with you in your head. Think about them but don't over think them and start second guessing, just do everyday activities like going outside, going to work (if you have a job), etc. and let the world influence you and give you inspiration. Some of the best authors out there have written their greatest books doing everyday jobs and writing pieces of the story during their free time. Sitting and pondering ideas in your head will just make it harder and has a better chance of changing the piece of work into something that you weren't going for. Just let the idea flow and grow on its own, don't force feed it.