I would add that writing it out, or preferably actually talking it out with someone, will take your ideas from the nebulous internal language of the mind, where they can be these indistinct perfect concepts that capture whatever it is you’re about at the moment… anyway, it will take them from that beautiful but unreal state, into real memes that have to be described with language and imagery and all its limitations.
The first time you speak your whole synopsis out loud, even if it sounds a bit hollow, that’s when you’re idea is born into the real world.