From Nathan Bransford:
One of the strangest things about writing fiction is that it often needs to make more sense than real life.
In real life, people fall into grief-stricken states of paralysis, wander around aimlessly without knowing what they’re looking for, and endlessly endure unpleasantness without trying to change anything about their circumstances. It’s extremely difficult to make those things interesting in a novel.
When we’re reading novels, it’s confusing and even frustrating when a character doesn’t act in accordance with their desires. To put it more simply: characters who care about something need to act like they care about it. They need to prioritize coherently (if not always rationally).
If they’re terrified, they need to act terrified. They shouldn’t be in the mood to stop in a place of danger and engage in endless breezy banter.
If they’re stuck, it’s helpful to see them at least try to escape so we can grasp the contours of their obstacles.
But there’s still plenty of room for humans to be human. One way you can give your character more latitude to act irrationally and convey to the reader that they really do care is to let their emotions spill out unpredictably.
A character under stress should act like it
Particularly when a writer has fallen a bit too in love with their dialogue, they can unintentionally create incongruities where it feels like a character can’t possibly care about what’s happening in the narrative if they are so unruffled that they have all the time in the world to engage in witty banter.
Now, this can be made to work. The James Bond-ish unflappable hero is an archetype for a reason. But the way to pull this off isn’t to show nothing at all getting to the protagonist. It’s to show stress building and then leaking out in unpredictable ways.
For example, a young protagonist who suffers an indignity from a teacher at school may not be able to immediately channel their frustration. If they were to lash out at the teacher, they’d get in still-more trouble, so they may well bite their tongue in the moment. But instead of simply moving on, the injustice should build and fester, and the protagonist might lash out at a safer target, like a friend or parent, or engage in some risky or uncharacteristic behavior. That acting out may well compound the stress even further.
In other words, the conflict isn’t just allowed to dissipate. It’s more like a ticking time bomb.
The most important principle here: Don’t let a good conflict go to waste!
Don’t let your character’s emotions just disappear. Pour them into an increasingly unmanageable bucket that might spill over at any time.
Link to the rest at Nathan Bransford