Defending
Defending yourself is to defend against the superego, whether
it is external or internal. The purpose of the superego is to
preserve the ego's point of view. The superego ultimately stops
you from seeing reality. Defending yourself is one method you
use to help you look at things objectively and without fear. When
you start learning how to defend yourself against the superego
you can't help but think in terms of having a self to defend.
Ultimately what is actually defended is the openness, the understanding
and the awareness. In time, we learn that understanding and awareness
are the best defenses. When the awareness is complete, there is
nothing to defend. (Diamond Heart Book 2, pg 146)

Defending Against Separation And Individuation
There is another, more fundamental, reason why individuals usually
revert to negative object relations, and especially negative merging,
in order to defend against experiences of separation and individuation.
To understand this reason we need to know specifically the nature
of the primitive affect that characterizes negative merging. It
has in it all the negative affects: anger, rage, hatred, pain,
fear, anxiety and so on. But there is a specific affect that is
always present, which characterizes negative merging and is independent
from the other painful emotional states. This is the basic painful
affect in the symbiotic phase, the feeling of frustration when
the child's needs are not met adequately and immediately. (The
Pearl Beyond Price, pg 253)