Okay, I have run into a problem. I am trying to write a new story, but every time I try to work on it, it falls apart. I have tried coming at it with different angles, such as slighty changing how it starts, what the ending will be, or just what the creature will be. I have the idea clearly in my head, but when I go to start typing I can only put in a few sentences before I lose it. I can't start on a new story till I get this one worked through because my mind just won't give up working on that one, and each time I try to start a different story, this one invades and derails my train of thought.
Anyone have any ideas how to get through this? I need some help or I might never be able to write another pasta.