Courage takes many forms in Bridge to Terabithia, whether it's standing up for girls' rights to run with the boys, crossing a rushing creek in the pouring rain, getting revenge on a bully, or comforting that bully. It's also about admitting when something scares you, knowing when to wait instead of fight, and learning that acknowledging or facing your fear is just as brave as not feeling fear in the first place. There are always going to be scary events and encounters, but what matters is how you treat others, not how strong or weak you might feel inside.
Ultimately, through examining his relationship with Leslie, Jess realizes that he's more courageous than he ever realized.
Through his experiences in Terabithia, Jess discovers that even the bravest people can be motivated by fear, and sometimes the most fearful people act most bravely.