Its a really good idea, an idea that you know that you can't afford to loose, if you put the pen or pencil down stop using the keyboard, all your ideas will just get lost in cyberspace.
Its in those moments of absolute inspiration that best stories derive from, even if the idea occurs in the most awkward place or time like work or school.
However as time progresses its the lack of craving attention, without it there is no drive to continue writing what seemed like a category 5 tornado to begin with, without that drive there is no will to go on, the question is how do you go on? That question lies within yourself, yes you, you are the one that gave the idea new life and form, only you will have the power to continue writing, what will give you that passion that driving force to do it all over again, whatever motivated you in the first place to begin writing that story.
Was what is it? The plot line, the characters, or a character, the middle of the story where you knew everything was just bursting at the seems.
Read your story and sleep on it, let the words crawl and seep through your skin, when your itching to wake up, or you can't fall asleep, its then you know that you have writer's bug, a bug that can stay for days, or weeks on its end.
I know from personal experience that I began an epic story 6 months ago, I had it planned for about 30 chapters, and I stopped about 6 chapters through.
I had a goal that each chapter was going to be 6 microsoft word pages long, I was going to write a chapter that was anywhere I felt the passion to write, and somehow mash it all back together at the end.
It didn't matter if the chapters seemed torn or rough, with careful thought and inspiration such things can be altered to make the chapters come together in perfect harmony.
When you write, you don't have to start at the beginning, I wrote chapters from the middle, some from the end and some from the beginning, as long as you have a plot and a story, its all you need to get started.
And let the passion run through your veins