I think the danger here is creating an idealized image of oneself (what Freud called the '
') that will still retainn some flaws one mistakenly regards as one's strengths or virtues, only now hypertrophied to supernatural proportions. In fact, if I ever occupied myself with HGA work seriously, I'd first look into tulpomancy and then try hard as hell
not to create such a custom-built entity unwittingly because my own specifications for such a being would be inevitably limited by my preconceptions as to what such a being could (or should) be like. I wouldn't want to create a 'mega-me' but encounter something completely different.
In my mind, the main advantage of considering your guardian angel an external and separate entity is that it could offer you perspectives completely different from your own. It'd be like talking to a close friend, a good therapist, or reading a brilliant book - you receive input from an
outside source which you'd have never thought of yourself coming from totally unfamiliar angles. In other words, I'd want my HGA to
surprise me instead of going over the same familiar old ground defined by me in circles. I tend to take the guardian angel concept quite literally: for me, it is an
angel, i.e.
neither me nor a perfected version of myself. Angels are said to be a superior being by nature, with quite different motives than humans and infinitely wise; on the other hand, I wouldn't entirely trust my own Higher Self because I'd still consider it slightly tainted by my own personal opinions, petty likes and dislikes, etc., although it should be above all those things in theory.
From a practical side, an externalized HGA could be conjured up like any other spirit, which adds another layer of 'insulation' against involuntary narcissism. I was very impressed with
Damon Brand's "Magickal Destiny" where you invite your guardian angel into your life and befriend it; I love his approach. However, the more you try to define the HGA in psychological terms, the more you disenchant it and conceptually constrict its nature, retaining control at all times where it's better relinquished from a certain point onwards.