Making oneself big or small

  It has taken me a while to figure out that anxiety hardly pays, though, in a sense, I believe that there is an emotional currency in it. When I become anxious, my body becomes very tense. In a way, this tension actually can give me the illusory idea that my body is more 'substantial' than it actually is, and in that sense I start to prepare for action. Sometimes, I have observed this kind of things with cats especially. If you ever see a cat that is afraid of a person or another animal, it will usually either crouch in a contracted body position, or it will try to make itself larger than it really is. The crouched position can give the cat a survival advantage by making it less visible and a little bit less vulnerable to attacks, while the larger position makes the cat more dangerous-looking. In both cases, one tries to give oneself a sense of having more substance with which to fly from the enemy or to perhaps attack. With anxiety, there is usually this sense of seeming more than one really is.
  It is interesting how, the less I try to base my existence on this feeling of 'being something', the less I feel a need to protect the body and person I identify as myself. It is much harder to do this, because one feels a lot more vulnerable. But there is not that much survival value to anxiety. For instance, trying to 'make myself big or small' in front of my boss just isn't going to do anything! Yet my body seems primed to do something when faced with even the anger or criticism of someone else.
    I think one thing to keep in mind with anxiety is that very little in life is a life or death situation.  One often imagines that it is, but the anxiety is just based on an illusory desire for a protected, more substantial feeling of the self as an integrated whole, ready for fight or flight. The funny thing is that the mind doesn't change with the changing moods or body position, but because one is so attached to the body or moods, it seems like one 'is' one's body when anxious. I think that in a funny sense, there is a craving hidden in anxiety, which perpetuates it. Although nobody truly wants to be anxious, the feeling of tensing up the body seems more bearable than a feeling of being otherwise exposed to some perceived danger. In a similar sense, I wonder if the 'sense of self' is not simply a holdover from our animal existence in the scale of evolution, when 'crouching low' and 'looking big' were associated with enhanced protection against predators. Just as I try to hide myself in isolation or try to look bigger than I am, so the twin poles of self-deprecation and self-aggrandizement serve to protect my body against perceived threats. Could one's 'self' have potentially evolved from these basic understandings of the body's relation to the world?
   I am not so sure if this theory is correct, but I am often curious to know what is the biological explanation or account for how the sense of self arises. Also, does this sense of how the self arises in nature perhaps help a person to let go of its illusory hold over the human psyche?