Treat others well

If we are in service line, we are told to treat customer well. We always hear " customer is always right".
But we do that because we want to gain profits from the customers. How about adopting the same attitude even if we are not in service line?
I think this is good attitude towards others not just the customers. Let me share with you the story.
Madam Tan is the lecturer on psychology in the university. She said her husband always shout louder to her but she talk to him in the soft mode.
Asking her can she change his husband 's attitude. She said that she was unable to change him. She said a person can be changed unless he want to change himself.