How does Juana support Kino through his failures?

Kino has a close connection with Juana. It is very elemental in that it is closely related to nature, family and universal bond,

"Kino could never remember seeing them closed when he awakened. Her dark eyes made little reflected stars. She was looking at him as she was always looking at him when he awakened... In Kino's head there was a song now, clear and soft, and if he had been able to speak of it, he would have called it the Song of the Family."

Juana is Kino's conscience and guide. The pearl of course disturbs this balance and he becomes abusive to Kino. Through Kino's failures, Juana remains loyal and always a reflection of a better way.

How does Juana and Juan Tomas' loyalty to Kino significantly leads to the eventual destruction of the family