The Refusal of the Call is a classic element in the archetypal Hero's Journey. Something happens which constitues a Call to Adventure - a circumstance or invitation crosses the hero's path, which requires the hero to take action. But in some cases the hero decides not to bother. It's too comfortable at home, or the journey seems too difficult or dangerous.
In the original film Star Wars, Obi-Wan invites Luke on an adventure. But Luke has too much work to do on the farm, and his Uncle Owen isn't letting him run off to have adventures. The Call only gets answered when Owen and Beru are killed by the Empire.
But even when dragged bodily into the adventure, one can still be reluctant and actively trying to refuse the call. Roleplayers generally play characters who never question what they're doing and if they want to be doing it. But you can get some depth by playing a character who doesn't really want to be there. Think Shaggy and Scooby in Scooby Doo. What if your thief isn't tagging along with the adventuring party because it's a good old frolic with lots of entertaining monster fighting and piles of treasure, but because it's a way to earn some money to pay off a debt before returning to his home town?
R2-D2: Seriously, just because Han supports it doesn't mean it's automatically a crazy plan.
R2-D2: All we have to do is kill Darth Vader—
R2-D2: —then dominate the clones with the Force, order them to kill the officers, and the Peace Moon is mi— ours.
Han: The Force? Hokey micro-organisms aren't going to save us now!
R2-D2: You forget, Luke is the son of Anakin. He can dominate the clones.
Luke: Small problem: I don't know how to do that.
C-3PO: He probably doesn't even want to.
R2-D2: Princess, you want him to use the Force. Convince him!
Leia: Not to capture a giant doomsday weapon for your benefit!
R2-D2: If this is a galaxy where using a biological mind-control hack to commandeer a planet-destroying superweapon isn't the most optimal course of action, then let me off, baby, I'm in the wrong galaxy.