What kind of guardian angel are you talking about?
According to the New Age, everyone has a guardian angel, usually a well known named angel, that watches over us. Even in the Left Hand Path, some people believe we all have “patron” demons, who, like guardian angels, guide us and watch over us throughout our lives.
If you are talking about the HGA of Abramelin, though, here’s the thing: The Holy Guardian Angel is NOT an actual angel in the usual sense of the word. Aleister Crowley himself wrote that he chose to call it that in his translation of Abramelin as a tongue-in cheek blind, but the term just stuck. It is something that is both simultaneously external to you, and a part of you.
Because it is not a being like the usual angels and demons we all know. It is beyond them, above them, and must be coaxed, like a lover, rather than forcibly summoned. It is the embodiment of the Divine, a Power, and requires one to “enflame thyself with prayer” to be brought into presence, and will come in its own time. Any “HGA” that can be summoned is not the same HGA talked of in the Knowledge and Conversation.
However, you don’t actually have to do a lot to make contact. Generally, you simply need to make room for it in your life. That is primarily what the prayers and purifications of the Abamelin Operation are for. You basically need to lift yourself out of material concerns and reach out for the HGA, and it is rather simple to do. We just have a tendency to mire ourselves in our physical circumstances, so that’s why the original operation required a retreat from the world.
I’ve just begun using the protocols of Damon Brand’s book Magickal Destiny to connect with mine, and they don’t require much effort at all. It’s all about intention, and a sincere desire for connection.