Here’s an interesting quote by William Walker Atkinson:

“Moreover, the experience of every individual will bear ample and generous testimony to the fact that certain persons, flowing over with vigorous nerve-force, will so radiate the energy that it is actually perceptible to those shaking hands with them, or even coming into their vicinity.

These individuals fairly radiate health and vigor, and exert a positive healing and invigorating effect, on those with whom they come in contact.

In a similar manner, is manifested a lack of sufficient nerveforce, by those unfortunate individuals who go around unconsciously absorbing the nerve-force of others, and, in extreme cases, becoming actual vampires sucking the vital forces from those around them.

Who of you have not met this last class of persons, and have not noted how depressed and weakened one is after having been in the company of such persons for some time?

The average person does not need any further proof in this case, beyond that afforded by his or her own experience.

It may be asked that if the nerve-force is inherent in the universal ether, and obtained from the atmosphere, why all persons are not equally endowed with this energy.

The answer is that the life-habits of individuals differ, and just as one is physically strong and robust, and another weak and delicate, so is one individual strong in nerve-force, and another weak in it.

Moreover, a change in the life habits of the person will inevitably result in a change in the amount of nerve-force absorbed and retained by him or her. While the object is the increase of your personal magnetism, you will find that at the same time your general health and vigor will improve.”