Some characters make choices he or she would prefer not to talk about, no matter how much he or she is pressed. Write a story in which your character is pressed to justify or apologize for his or her behavior. The level of pressing from the other character is up to you; could be passive-aggressive, the sort of pressing one might even be hard-pressed to recognize. Or could be the “bad cop” in an interrogation is right in his or her face. Or maybe there’s no pressing at all; when your character expects to be grilled on his or choice a little bit, it doesn’t come – how does your character respond to that?
Write it up and see what happens.