The character that obsesses probably sells better.
Those characters stand out.
At least that’s my observation from years of analyzing novels, short stories, and scripts.
If our main characters (protagonist and antagonist, and often a sidekick or two) aren’t worrying about something, then what’s the point of the story?
Obsession or obsessing over something means gnawing on a topic. It’s more than normal worrying.
Plots that depend on revenge usually require a character obsessed with getting something and usually by some deadline.
Obsession usually haunts a character. Obsession can be liking, hating, loving, plotting, planning, acting. And it doesn’t let up until there’s some resolution, usually in a big climax moment.
Obsession = Pressure.
Don’t mistake “obsession” with “mere need.”
An obsession festers—or blossoms. It grows in a story.
The obsession is like an electric current always flowing within the character, antagonist or protagonist—or a secondary character. It has to be contended with all the time. The mistake I sometimes see in manuscripts or scripts is that a character starts creatively with an obsession, but the writer leaves it behind in the first act as if it were only worth a “funny moment” or relegated to “the hook.”
Every genre (such as thriller, romance, mystery, historical) has excellent novels that show how obsession works.
In reading our best thrillers, the protagonist and antagonist don’t let go of that “do-or-die” need easily.
A sweet romance may have a character obsessed with changing or accomplishing something, even apart from the romance unfolding. That makes the character three-dimensional.
Typically we think of villains as the ones being obsessed but notice I’ve mentioned other types of characters, too. Obsessions can be fun and funny. A writer who thinks they lack the humor gene only needs to invent an obsessive character to bring in funny business.
If the obsession is solved or left behind by the midpoint, the story usually stalls, though another character could take up the obsession. Even a villain can be killed off at the Midpoint and then his buddy steps in and is worse.
An obsessed character need not be in a lot of action. What if they just sat or stood? They might reside in a prison cell the whole time, like Hannibal Lecter, from The Silence of the Lambs by Thomas Harris, book and movie. He was obsessed, certainly, and he gave us the creeps—which we loved.
We also know an octopus in an aquarium obsessed with escaping and we admired him for it and rooted for him. (Remarkably Bright Creatures by Shelby Van Pelt, book and movie.)
Obsession is a layering on top of “need.” Obsessed characters often use all five senses and ACTION to try to get what they need. They do not give up.
There’s the formula for you: A high NEED, all five senses ON ALERT, and they are compelled to go into ACTION and stay in action to get what they need.
Obsession can be funny or soft, romantic, cute, or the gut-wrenching opposite—whatever your story needs and what you enjoy writing.

