Another meditation: "You must first be your own."

[vervex]

I think those ARE the principles of "magical self-defence," well developed sense of self allows you to be free from the manipulations of others.

This. I'm not sure what you mean in regards to the "magical" part of self-defence, that being said, Spaced got it right; by knowing who you are, your core identity, and by being in tune with your emotions and thoughts, you will not be manipulated or influenced by others. When you are standing on solid ground, you will recognize manipulation or influence for what it is, and you will be able to say no; you will also understand why you say no.

There is no magic in what I describe however, simply the knowing of oneself.