Every aspect of creation is governed by an angel. Even trees and plants (especially those with healing properties) have angels supervising their growth. As the Sages said [Bereishit Rabbah 10:6] "There is nothing below, not even a common herb, which does not have an angel on high that strikes it and tells it to grow". Each of these angels receives its life force from the particular Utterance which is the source of its creation. It then transmits a measured amount of this life force to its particular charge.
This power of the angels to receive and transmit life force is referred to as the power of the "hands". (The Hebrew word for power is ko'ach, numerically equal to 28, the number of bones contained in the fingers of both hands). With its "right hand" an angel receives life force. With its "left hand", it dispenses the exact amount needed to its charge below. This is the meaning of the Sages' statement: "he strikes it and tells it to grow". "Striking" is done with the angel's left hand (for the left side represents Gevurah, judgment).
The Torah tells us [Proverbs 4:20-22] "My son attend to my words, incline your ear to my utterances.... For they are life to those who find them and healing to all their flesh." We learn from this that all healing flows from G-d, through His Torah. The Torah is the source of the [healing] power of the angels, who in turn transmit it to all the various herbs in their charge. This power is manifest when one accepts the Torah and has faith in the Sages who reveal it, for the Torah was given over to the Sages, and one who deviates from their teachings is called "he who causes a breach in the wall [of faith].
This is the meaning of the injunction [Deut 17:11] "Do not deviate, neither to the right nor to the left, from what they teach you". If you deviate to the right (tending towards unnecessary zealousness), your angel's "right hand" (ability to receive from its corresponding archangel and Utterance) will be hindered. If you deviate to the left (by transgressing the Torah), the angel's "left hand" (ability to transmit) will be hindered.
Of course, the removal of your angel's hands means that you cannot receive your healing, for without an angel to bestow the life force upon it, the herb upon which your healing depends loses its power to heal. Thus, the degree to which a person is attached to Torah determines the degree to which he is able to be healed.
Source: "Anatomy of the Soul" - Chaim Kramer
from the teachings of Rebbe Nachman