I've had it all my life and have found that it's greatest "source" has been food sensitivities due to leaky gut due to candida overgrowth in the intestines. So candida (a fungus) needs to be dealt with. I do that with the Candida Zapper. Of course I still need to be careful of what I eat and not subject myself to much stress (including vigorous exercise). Candida, on top of causing leaky gut, toxifies the body with its metabolic byproducts which makes a type of chemical stress in the body and makes you tired and confuses your thinking (due to an alcohol like substance it produces). It also causes depression.