Just a moment ago, I posted in here Timothy Roderick's excellent shadow mask meditation. It is an excellent object lesson in how "dark" magic is not all evil. Dark magic deals with the hidden things, it is the true occult art. Mr. Roderick is not the only person to refer to the shadow aspect of our selves.
A wise witch will always strive to accomplish one of the exhortations that is reputed to have been at the temple of the oracle of Delphi: Know Thyself. This includes knowing the parts of yourself that you are not comfortable with, confronting the lies you tell yourself about who you are, and recognizing all the elements of the past that influence you. In the same respect, we will also work to accomplish this axiom's advised goal: Physician, heal thyself.
The shadow self is the elements of who we are that we repress and strive to forget they exist. We may try to hide from our latent fear of thunderstorms or that horrible and terrifying memory of the car accident we were in as a child. These things carry forward through time if they are not addressed and incorporated into our psyche. The latent fear of thunderstorms may develop into a phobia. The terrifying memory may turn into major problems learning how to drive. Either way, the hidden things will make their presence known.
Why do they make their presence known? Because they are a part of you and until you can accept and move forward with that fact, you will struggle with it. The goal of witchcraft is to be healthy and wise, to become a self-actualized person in control of their life. Magic is but a tool. Psychology, proper diet and exercize, and herbalisim are other tools that are available to a witch to accomplish these goals. It is the state of harmony that results from a healthy spirit and psyche that brings us into communion with the Gods because that harmony results from recognizing the divine in ourselves.
I have flashes of it and I'm filled with a mixture of awe and fright at times by that. But it's the times where it is as natural as breathing that I strive for. When I can recognize my union with the Gods, my intrinsic value, and all the other important things about myself, I will perhaps then be willing to say that I am wise. Until then, I'm still a student learning. I may be helping others along the way, but I still am learning as well.