Wow: This, from Ira Glass of This American Life, hits home.
You have an idea. This could be a great story. You can see it, feel it, taste it. You report, write, revise. You finish and think: That's not what I wanted it to be. You deflate.
But you can't stop. You have to keep trying to execute those ideas, because only in doing that, over and over and over, can you ever get closer to the actual vision you see in your head when you think, This could be a great story.
Glass puts it better here, and lets you know: You're not alone.