We are what we think. All that we are arises with our thoughts. With our thoughts, we make the world.
That’s attributed to Buddha. So how does it apply to your characters? Think about how your characters’ perceptions decide what they believe is true. But you, as the author, know if they are correct. When is it better for your story if your character is wrong?
Look at the last thing your character thought. Was she right? What if…she wasn’t?
Look at the last thing your character did. Was he convinced he was on the right track? What if…he wasn’t?