Everything rotates around definitions. So this is the shortened version of mine............:)

The primary purpose and function of the ego is to enable our self-preservation. This function must assume ever-present and possible danger. i.e. it thrives on fear.

Spirit and fear are not compatible. A predominance of either drives the other out(or greatly lessens its effect). It can either be spirit drives out fear or, reversely, fear drives out spirit(love)