Man isn't just a collection of cells. The basic nature of man is spiritual. We are individual "life units" in a physical bodies. This life unit is capable of emitting either white(positive) or dark(negative)energy.
The white energy can be directed at any body part with the thought "I feel alive". Often, this will produce a warm feeling or a tingle sensation. Some healing may occur.
In a similar vein, negative energy can be taken out of a victum's body as grief.
Different holistic practices approach spiritual healing in different ways. One uses the technique that works for him. Energy fields are not the same from one human to another.
We are either putting positive or negative energy in ourselves or others. On a physical level, this could manifest itself as wellness or sickness.
http://www.crystalinks.com/healing.html (More Information On Spiritual Healing)