Mental focus is said to be one of the most effective healing modalities availabe to us.  It has been proven that a person's cognitive and emotional processes have a profound effect of our health.  When you meditate, your rational thought processes, housed in your cortex, begin a dialogue with your brain's emotional centers, the hippocampus and amygdala, both of which are in your limbic system.  When the cortex and limbic system agree that it is okay to relax, they send the message to the hypothalamus, which connects the brain to the endrocrine system.  This releases calming neurotransmitters and hormones which calm the body.  The immune system then kicks in releasing its own molecules of information which completes the healing process.  You then shift into a relaxed alpha brain wave pattern, and your nervous system is dominated by the parasympathetic branch.  When this happens even more nerve signals are sent to your organs and glands of immunity.  You then reach the ideal condition for healing(Khalsa, 2001). 
Disease is exacerbated by negative mental conditioning and can be impacted successfully with positive mental conditioning.  Try repeating the mantra, "healthy am i, happy am i, holy am i" and see if it improves yokur disposition.