Joshua 1:9

It opens with a question, and the question is the strangest part. Haven't I commanded you?

Courage is being issued as an order. That is not how we normally think about it. We treat courage as a temperament — some people have it, some don't, and telling a frightened person to be brave is about as useful as telling them to be taller. But an order implies the thing ordered is available, and that it is a matter of choosing rather than possessing.

What makes it possible is the second half. Not you are capable, not the odds are better than you think. For Yahweh your God is with you wherever you go. The courage is not being drawn out of Joshua. It is being justified by a fact about his company.

And wherever is the word doing quiet work. Not in the battles. Not in the places I send you. Wherever you go — including places he should not go, including the retreat and the mistake. The promise is not conditional on Joshua getting the route right.

Notice also the repetition. Four times in nine verses: be strong, be courageous. Nobody says a thing four times to someone who is already convinced. The repetition is evidence of Joshua's actual state, and the text does not hide it. He had watched Moses do this job for forty years and knew exactly what it cost.