Why I think the short form and novel form are similar:
This morning NPR hosted a Broadway composer interviewing two other Broadway composers about their process and experience with creating, music, and collaboration. One of the composers spoke of his experience playing piano from the age of four. He said he had a classical background, and then at about 12 or so he started to add in current pop music and jazz. He said all that gave him a wonderful foundation to draw on.
I feel, via a little research and deductive thinking, that within the short form lies the foundation of all storytelling. Poetry, fables, fairy tales, and even Bible stories a length conducive to telling a tale fireside. Obviously there are exceptions to this, but even longer tales were broken down into what has become our modern day chapter, for ease of telling.
Modern cases in point: most films are, if converted to prose, short story length. (One of the more noble reasons the final Harry Potter novel will be cut into two films--if rumor can be believed.) Ditto with stage plays. Interestingly, I once had someone argue with me about subplots in those forms, and I argued that really great short stories carry subplots, if you look hard enough.
But they are simpler, and that's the point. Mastering a three-act plot, or the five-part plot, or whatever you like to call it, hasn't been easy for this writer. In fact, I'm struggling with it in the WIP right now. But at least I recognize that there's an issue. Have I mentioned it's my FIFTH novel? By some arguments, I've written enough novels to be an expert at novel writing, and yet, I didn't really catch onto it until I started writing short fiction.
Short stories put all that into a manageable form for me, something I could complete in days or hours, making the rise and fall of tension and plot events easier to discern.
I'd never say this is what it takes for every writer to become a successful novelist. But it's worked pretty well for this one, and I really don't count myself as anything particularly special.