One unavoidable difficulty of trying to put optimizing sparks inside your characters is that none of the characters want your plot to happen.

You want the hero and villain to struggle heroically. Or maybe there’s no primary antagonist and the hero is up against Nature, or themselves, or has to resolve a romantic confusion. Regardless, if the protagonist encounters no obstacles on the way to getting what they want, you have no story.

But the protagonist does not want your obstacles. The protagonist has watched their own share of romantic comedies and is making sure to communicate with their crush. The villain wants the heroes to die in chapter 1, and sends extra troops to make sure it happens. Every Level I Intelligent character wants to take your conflict-driven plot and throw it out the window.

That’s what takes the brain-sweat. You must so cleverly craft every character’s situation that, given what they know, their inner spark’s output works for your plot.

He references HPMOR several times, so there's a link if you're curious. One of my favorite pieces of fiction, ever.