On the Spiritual Level

We are alive because life force is flowing through us. Life force flows within the physical body though pathways called chakras, meridians and nadis. It also flows around us in a field of energy called the aura. Life force nourishes the organs and cells of the body, supporting them in their vital functions. When this flow of life force is disrupted, it causes diminished function in one or more of the organs and tissues of the physical body.

The life force is responsive to thoughts and feelings. It becomes disrupted when we accept, either consciously or unconsciously, negative thoughts or feelings about ourselves. These negative thoughts and feelings attach themselves to the energy field and cause a disruption in the flow of life force. This diminishes the vital function of the organs and cells of the physical body.

Reiki heals by flowing through the affected parts of the energy field and charging them with positive energy. It raises the vibratory level of the energy field in and around the physical body where the negative thoughts and feelings are attached. This causes the negative energy to break apart and fall away. In so doing, Reiki clears, straightens and heals the energy pathways, thus allowing the life force to flow in a healthy and natural way. 

Reiki can never do harm. It always knows what a person needs and will adjust itself to create the effect that is appropriate for them. One never need worry about whether to give Reiki or not. It is always helpful. In addition, because the practitioner does not direct the healing and does not decide what to work on, or what to heal, the practitioner is not in danger of taking on the negative energies attached to the client.

Reiki is a channeled healing, so the practitioner's energies are never depleted. In fact, the Reiki considers both practitioner and client to be in need of healing, so both receive treatment at the same time. Because of this, giving a treatment always increases one's energy and leaves one surrounded with loving feelings of well-being. 

Paraphrased from reiki.org