Remember your chemistry lessons from a long long time ago. At some moment you would discuss acidic and alkaline substances and how they balance eachother out, also there is a value or indicator referred to as the Ph value.
There is a state of neutrality in nature and in your body actually. Your body needs a neutral Ph value.
Unfortunately you can be put out of balance and leave you body in an acidic state. And that is not good for you. When in an acidic state your body cant heal itself. When this happens over a longer period of time you are setting yourself up for potential health issues.
Why and how; well there seems to be an initimite relationship between cortisol (stress) and the body's Ph value. Also your diet has an influence. Basically all processed foods are at the acid scale and your leafy greens on the alkaline scale. Rule of thumb is that one s diet should be 80% alkaline.
..what well help most though; try to live a happy live.