To observe is to not identify with any negative psychological element within the three brains.

By observing the three brains, we save energy, since those divine forces that were once consumed through feeding desire now become transmuted into light, comprehension, and peace, and are thereby conserved for use by the Innermost.

This, in itself, helps to fortify our three brains with superior forces, so that it is harder to identify with negative circumstances or internal psychological elements like before, when we never knew of these practical teachings.

We also learn to fortify the three brains with Christic energy through our esoteric practices: meditation, runes, pranayama, sexual alchemy, sacred rites, mantras, etc.

To fortify is to defend, as in a fortress being prepared against an onslaught from enemies. Therefore, with harnessing sexual energy through different exercises, we prepare our three brains to defend ourselves from the negative attacks of our worst enemy: the ego.