One detail from "A Cub Pilot" that helps shape the central idea that if you believe in and trust yourself, no one should be able to shake your confidence is the protagonist's determination and resilience in the face of challenges. Throughout the story, the protagonist faces numerous obstacles and setbacks while learning to pilot a steamboat on the Mississippi River. Despite these challenges, the protagonist remains confident in their abilities and continues to persevere. This detail illustrates the importance of self-belief and trust, as it shows that even when faced with difficulties, having confidence in oneself can help overcome obstacles and maintain a strong sense of self-assurance.