Just the other day I heard Chris Hardwick's Nerdist podcast from last year in which he interviewed Neil Gaiman, and I was interested to hear Gaiman liken the process of writing to laying a brick wall. Essentially, he said that each word is a brick that you're laying on top of all the others, and how strong the whole structure is depends on how well you've fit the words (or bricks) together.
I like the analogy, since I've been thinking about writing in a similar way for a while. Now, you can liken writing to any number of things: Joe Abercrombie refers to plotting as architecture or gardening, depending on how comprehensively you do it at the start; Haruki Murakami wrote an entire book drawing the parallels between writing and running marathons; and Marcus Sakey manages in a single blog post to liken writing to house painting, relationships and children. I list these examples because I think they're all absolutely right, and because I've thought of writing in each of these terms (uh, apart from house painting or children).
When working on a novel, I've frequently visualized it as a structure that I was creating, from the foundations up to the walls and roof, the foundations here being the premise and setting and the characters. If these aren't done properly, or don't fit together well, then you can't build the action on top of them, which means you can't get to the end you've envisioned (ie, putting the roof on).
Now, what Abercrombie was describing related more to the actual outline of a novel, but I think his analogy is valid, because the way he outlined it influenced how he wrote it. In his view, architecture is when you lay everything out as clearly and exhaustively as possible from the start, so that all you need to do next is fill in the blanks with dialogue and sex scenes and what-have-you. On his own blog he's detailed how he switched to more of a gardening approach for the novel he's currently writing, which meant he just arranged everything in the broad shape that he wanted and tried to grow a bunch of things on that arrangement. I read his comments since then to mean that he found the transition to a more free-form type of plotting difficult - the proof, I suppose, will be in how well the finished novel reads.
(Incidentally, Stephen King is famously disdainful of really rigid plotting, as he feels it's too restrictive. It's clearly a subjective issue, as on the few occasions when I've tried to plot a long-form story a little less rigidly I've come up against obstacles that caused me to abandon the project altogether.)
The running analogy is another one that appeals to me, because I also run long distances. I've done a few 10ks and a few half-marathons, and I'm training for a full marathon later this year (in fact the idea for this post came to me while I was out running this morning). In my experience, long-distance running is pretty intimidating if you've never done it before, but once you've done it you see that it's actually pretty simple: you just keep putting one foot in front of the other until you get to the end.
It's not hard to see how this applies to writing. Once you've written a few stories or finished a whole novel, you realize that the key is just to keep writing words, one at a time, until you're done. Moreover, the length of what you're writing changes how you approach it: once or twice I've had an idea for a story and then dashed it off all at once, just like I got through my first two 10ks by practicing running for an hour at a time. However, now that I'm training for a full marathon I've been told by those who've done it that there's a more strategic element to it, and the training is more regimented. Just like with writing a novel, it's not advisable to just start doing it until you're done (again, pace Stephen King); you need to plan out how you're going to get to the end.
I'd also like to point out that I've learned training properly - ie diet, weights, etc - gives you better results than just hitting the road for increasingly long stints each week; just as in writing it's better to actually learn how to structure a narrative, flesh out characters and write dialogue than to rely only on your natural genius to carry you through each time.
The final analogy I want to look at is writing's similarity with relationships. This is maybe a shaky one for me, since I'm by no means an expert on dating or relationships, but indulge me: starting on a new novel is like getting a new girlfriend, in that you just want to spend all your time with it in those heady early days. I started on a new project last year (incidentally at the exact same time I started going out with somebody new), and managed to finish the first draft in just four months - by the end I was averaging around a thousand words per writing session (by contrast the relationship with the girl fizzled out after a month).
Fast forward to now, and I'm coming up on the end of the second draft. This has been much more work, in part because I've set myself a minimum number of words per chapter, to get the whole book up to a publishable length (you wouldn't believe it from this blog post, but my writing is extraordinarily concise), but also because I've been fleshing out characters, places, histories. These days I'm lucky to write more than six hundred words at a sitting, let alone a thousand. Which isn't to say I'm not enjoying it - but the initial excitement of being constantly between the sheets (of paper) has given way to something I have to actively work on, if I want it to progress to the next level. If I knew I didn't love it I'd stop and look for something else to do.
So to wrap up, where does Neil Gaiman's brick-laying analogy fit into all of the blather above (pun intended)? I'd say it informs each of the other analogies in its own way: as with architecture, it's all about making sure all the pieces fit; like running it's something you do one step at a time; and like relationships it's something you can't just ditch when the going gets tough.
But it also stands on its own, on a stylistic level. It's not enough that you've written 80,000 words - they also have to be damn good words. And that's where the questions of fitting them all together, and using the right materials, and having the right training, come in.