Here is my one top tip to building fictional characters: their greatest strength should also be their biggest weakness. There are some quizzes that circulate on the internet, like this one, that purport to tell you what people secretly hate about you. There are always a bunch of silly questions thrown in about picking your favorite animal or your signature dance move, but the meaty questions, the ones that determine the answer, are the ones that ask you what people love about you. Because whatever trait it is that people love about you, that’s also the one that drives them nuts.

If you are charming, gregarious, and the life of the party, chances are that other people read you as shallow or self-involved. If you are quiet and reserved, like me, you probably come off as cold or snobby sometimes. Also apparently scary, from what I’ve been told! A person who’s a smarty pants may save the day in times of crisis, but on a regular day, some folks find him to be a giant know-it-all.

This push-pull of your best and worst traits holds true for fictional people as well. Characterization is most satisfying when it is rich and consistent. So if your character has a tendency to act first and think later, she might shine in an action sequence but create friction with her boss. Similarly, if your character believes passionately in the bonds of family, he’s probably willing to make huge sacrifices for those he loves—but may be blind to their faults.

Characterization is also situational and relational. You don’t act the same way with your mom that you do with your friends, or with your boss. There are always shadings and exceptions and times when your actions may surprise even you. I have a petite, mild-mannered friend who chased a male intruder out of her home when she caught sight of him. She never would have imagined she’d do such a thing until she found herself shouting and running after him!

Broadly, though, who we are in terms of our core personalities don’t change much over time, and the things we do well, whether that’s socialization or analytical thinking or caretaking, have a cost to them. Considering this inherent yin-yang when building your characters can help you mold them into believable, complex people.