How do Juana’s actions stop their panic flight?

I really like this scene. The beauty of it is she doesn't really do anything;Juana's strength comes from within her,

"He looked then for weakness in her face, for fear or irresolution, and there was none. Her eyes were very bright. He shrugged his shoulders helplessly then, but he had taken strength from her. When they moved on it was no longer a panic flight."