Guardian is a symbol of protection and restriction. Antiquity assigns guardians to ancient shrines and groves. It is believed guardians protect the unprepared from gaining access to things that would be dangerous in their hands. Dragons or gargoyles and myth heroes have represent guardians at times. For those Traditions in modern neo-Pagan Witchcraft and Wicca that have the office of guardian the duties are training to become a High Priest, assisting the High Priest, and protecting the High Priestess and the Book of Shadows of the coven.
The guardian, in another sense, is the conscious rational mind standing watch over the subconscious mind. The guardian here is synonymous with rational reasoning. Chiefly it prevents intuitive thinking by causing many emotions and hunches to be mistrusted or completely ignored. Frequently experiences are dismissed as figments of the imagination. This can be disastrous in many occult activities such as meditation, contemplation, and dream analysis. A.G.H.
Source: 78, 169.