The Holy Guardian Angel is a concept that is somewhat unclear to most, so I decided to write up a quick little thing to explain my insight on it, and other aspects of your 'self'.
The HGA, isn’t holy, a guardian, or an angel. It is your perfected self, the ultimate amalgam of all your selves united and reconciled as one.
The lighter self is the most ‘light’ or selfless version of yourself, which from your perception of ‘moral good’ is derived.
The darker self is the most ‘dark’ or selfish version of yourself, which from your perception of ‘moral evil’ is derived.
What I propose is simple, your darker self is inherently that which you would become if you absolutely abandoned what morals you may follow, and your lighter self is what you would become if you followed your morals to their logical end. The perfected self is what happens when you reconcile both your lighter and darker selves within yourself in a way that is non-contradictory. Seeing how the lighter and darker selves by their nature are opposites, and thus contradict each other completely, you can see why you may never become your perfected self.
The beauty of this is that you have the free will to choose your own path, for your own personal light or dark, or even tread the middle. Heck, if you wanted to, you could reject both your lighter and darker selves and change utterly on the most basic level, although that way is what I would consider madness.
And as Crowley said, Do what thou wilt shall be the whole of the law, so ultimately, what you do with what I propose is up to you.
The assertion of the Higher Self and the HGA being the same is a very modern and, in my own experience as well as traditional scholarship, a very wrong one. Abramelin, Agrippa, and even Crowley (in his later years, when he had more experience with the thing) generally agree that the HGA is a special entity separate from your higher self but assigned to it. It is “holy” because it is innately above the influence of the stars and planets, which gives it much greater freedom and power than most other entities. Agrippa even explicitly notes at least three guardian spirits available to every man who does the work to establish contact: the spirit governing your profession, the Natal Spirits assigned to you at birth by the stars and planets, and a “holy” spirit that lives in a realm above the influence of the planets.
The work of the HGA is entirely separate from the work of Self-Realization, which itself is not quite as simple as combining your Id and Superego.
I personally see morality as rather subjective, thus I use terminology a little differently. 'Dark,' to me, would rather signify that which is hidden. One's subconscious, for instance. Potentially the 'Shadow Self,' if you wish to refer to the work of Carl Jung. Thus, it is the goal of the magician to bring that darkness to the light, or to make the unconscious conscious. This sort of gets into achieving things such as Gnosis.
All I now is radiant heat energy is warm and it’s absence makes me cold. Man likes beingwarm for the most part and able to see. A lot of life forms thrive in it as well. What we can’t see in the dark terrifies some.
If there are these higher forms why is there not opposing forms to drag us down in the cosmic balance scale?