The Sun in our chart often shows what we desire and what are essence is in life. When located in the 6th House, there's a tendency towards paying attention to the small things in life. You find satisfaction by doing mundane tasks and giving people a good hand or service. Often, these people like maintain a strict schedule by getting up early in the morning, paying careful attention to health and diet, and making sure that their responsibilities are always met.
Having the Moon opposite in the 12th creates a contradiction with your Sun. The Moon represents our comforts and motivations. So in a way, you struggle with this daily activity stuff. Moon in the 12th points to a private life, spirituality, and avoiding the world or escaping.
You know how guru's or yogi's or those people that just sit and meditate hours and hours a day? Those are the 12th House people. They do not worry and stress over the small and material matters that is represented by the 6th House.
Your Moon feels comfortable in this kind of lazy, meditative, escapist state in the 12th. Your Sun, however, wants to serve people and to take responsibility. The Sun represents what we want; this is what you want; this is your life. You may be comfortable doing 12th house things, but what will fulfill your ego and sense of worth in this life is by taking responsibility in life.