Left or Supportive
If you this is your main arm, the left or supportive arm is nearly always used to denote the unconscious, habitual or supportive parts of yourself; things outside your conscious ego, darkness, ignorance, devolution, the forces of destruction, the earth. For instance your less used hand supports the action of the main arm in most activities, such as writing, hammering a nail, etc. So the supportive arm can relate to your confidence, all the subtle feelings and skills that together support the actions you do in the world.
The supportive arm may also represent those parts of yourself that are not predominant. The desires and urges that are not allowed the major role in your life. In some dreams there is a play on what is right/main (correct), and what is left/supportive (wrong).
A few people might also find that in some dreams one side of their body represent the feelings and attitudes they absorbed from their mother, and the other side what they absorbed from their father.
The play between the main and the supportive is sometimes used in dreams to illustrate the dynamic action between opposites in our own nature. For instance the play between what we consider, from our cultural upbringing, to be right and wrong, good and bad, constructive and destructive. Although the terms good and constructive may help us make useful decisions, sometimes the way to real growth is a balance between the opposites.
Your internal world of feelings, memories and values – the supportive; your external world of activity and environment – the main. A secondary choice – left/supportive; the ‘right/main’ choice at the time. Parts of self unconscious or shadowy – left/supportive; your conscious known self – right/main. The immoral, selfish, wrong action – left/supportive; the moral, right action – right/main.
But the supportive or left, if you are right/main handed, can also show the usually unconscious or wonderful and wide inner world of experience – an inner world in which we might find incredible meaning and abilities. See the dream below as an example.
I have had a few wonderful dreams lately. Very short though. In one I was leaning over a person who was sitting. It was my left arm that dominated the dream (I am right handed). It was gold and glowing. The other I reached into a glass of pure clear water with purple petals through it and I felt pure joy.
See Jill Bolte Taylors extraordinary experience when her usual ‘right handed’ personality was knocked out. http://www.ted.com/talks/jill_bolte_taylor_s_powerful_stroke_of_insight.html