The general cause of disharmony within a body system is disharmony within an entity’s thoughts. There are very toxic thought patterns that can be guaranteed to result in a less than optimal physical configuration.
Thoughts of fear drive out peace. Thoughts of love build up inner peace. It is as simple and as challenging as that. As your mind, so shall your body go.
That which you worry about, that which you fear, you call to you. We would encourage you to watch your thoughts like a hawk. When you find them becoming toxic, ask yourself to stop thinking along those lines. Ask yourself how your highest and best self would approach the situation that has you in worry and fear.
When that thought comes to you of what the highest and best would be, try it on, my friend. See if it feels more comfortable to you, more profitable, more skillful, and more helpful than your fearful thoughts. This is the kind of choice which does not look like a choice of polarity, but it is. The choice of fear is the choice to have life be about you. The choice of love is the choice to have life be about the one infinite Creator.