There are a couple of things I learned from his book, and I'd actually recommend reading it if you haven't. As a writer, though, the biggest thing I learned was to:
FINISH YOUR NOVEL
Sparks wrote about his first experience writing a novel, and how it was grueling, and hard, and at some point you want to just quit because what's the point?...He admitted that when he finished it was complete shit. He, NICHOLAS FRIGGIN SPARKS, knew it was shit.
But that's not what mattered.
What mattered was the fact he was able to write a friggin novel. And if you're able to sit there, shell out a novel, even a crappy one...maybe you can shell out another, and another, and eventually find an agent, find a publisher, and start getting yourself out there. Or, even if you're taking the self publishing route, you still need a FINISHED product to be able to put out in the world.
After I read his book, I finished Confessions of an Immortal Heart...crappily. To this day it still needs editing and it's been solidly done for a few years now. I finished a novel that ended up being about 76,000 words. On days when I need a good laugh, I go back to the very first draft, because it's so poorly written there's nothing else to do. On days when I doubt my ability as a writer, I pull it up, and look at the page count because I did this, I accomplished this. If that's not enough, I pull up Igniting a Firestarter, or Character Defects, because I've written three novels. I have a very high word count...and if I start reading what I've written, I'll find lines that I really like, or the editor in me will come out and strengthen what is on the page. And then I know...I'm a writer.
I've written three novels because I finished one. If I hadn't finished one...I'd be living on a beach...with nothing to show for it...(Don't get me wrong, I'm still living on a beach :) )
Moral of the story is: Push through, work hard, and finish. Especially if this is your first novel, finish it. Once you have the confidence that you can finish.....
(I'm gonna be corny here, are you ready?)
...YOU CAN DO ANYTHING.