Nervousness appears to be a psychological problem. It seems to be associated with the fear for various things, such as fear of failure, fear of death, fear of bankruptcy, etc.
When this happens, the heart starts beating rapidly, resulting in palpitation.
The latter is induced by an increased secretion of the male sex hormone called androgen, which is produced by the adrenal glands, situated above the kidneys.
The palpitation decreases with increased intake of cooking salt (sodium chloride). Normally, all Skeletal and Thin category persons take plenty of salt through their foods.
They also consume abundant water (e.g., >3 L, daily) and urinate liberally (>12 times/day). Since salt is highly soluble in water, most of it gets lost in the urine.
This results in salt inadequacy and increased production of androgen, giving room for increased nervousness.
Therefore, one can notice that all Skeletal and Thin persons tend to be short-tempered and highly sensitive all the time.
My study has shown that all the obese people always prefer to take very little salt.
Yet, since the obese always under-urinate (2-3 times/ day), their body tends to retain any little salt they may consume, which over a period of time, accumulate to reach to a very significant amount, resulting in (a) the reduction of androgen production and (b) the increase of blood pressure.
The reduction of androgen output in the obese, reduces the rate of heart beat, and that in turn reduces the nervousness and anger in them. Most of the obese are normally cool-headed and relatively insensitive.
See Palpitation, and Tension & Stress.