Writing the Too Big Story

Many of us have this problem: every story we come up with grows to novel size even though we're trying to keep it short. I gave some more thought to 'Skyman' and all the things I came up with seemed to take the story well out of the 10000 word range. I know it needs more filling out in order to become a complete tale but I'm not yet sure how much I want to put into it. Anyway, another thing this points out, to me at least, is that I'm now at a point where I can start to visualize how many words it takes to tell a story. When I think of ideas I seem to have a word count running alongside my train of thought. 5000 to work through this situation, 2000 to set up this side character's arc, etc. I think that's an important tool for writers. How many times have we started something and realized that the idea couldn't be captured in a nice neat bundle? It happens to me a lot, except now it happens in the idea exploration phase which handily saves me a lot of wasted writing.