Sometimes as a writer the voices in your head take over your life and there isn't anything to do but write. Despite all the wisdom of the published in having outlines, applications for characters and plots, sometimes a great story starts out just by being written.
The more passionate you are about something, the stronger you feel that urge to express yourself, the better your writing is going to be.
Yes, after that initial pouring out onto paper comes the editing, and the smoothing of the rough edges. Sometimes you only get a piece of the story, but from that piece you can discover a plot, uncover all the characters you need and further the idea.
The point is, once again, to write. If you aren't writing, the voices inside cannot get out. Bottling them up inside just causes stress...and stress is a killer, don't cha know.