It is my perspective that when a witch initiates within a red-thread, an initiatory House or living lineage, that tradition becomes embodied within them. It is an incredible responsibility, and one that is forever.
At my Faery Tradition initiation, while waiting for the initiates to come get me, I was having very intense visions and I became aware that they were busy "gathering up the whole cosmos" so that they could then "put it inside me." I was keenly aware that when I married God Herself, I would become one with Her at the moment of Creation; that eternal, perpetual Moment we call The Sabbat. At my adoption into the clan, all of those witches who have come before me were now given new life through me; just as with all of the Ancestors whose chain of being have made us. This is the witch-blood.
I knew that I would rebirth the tradition that fateful night, just as each and every initiate does at their own initiation. For me, this is what constitutes a "living tradition."
It lives within us, which is why it is perennial, perpetual, changing its shape to live on through each of its initiates. I believe that any red-thread does this, which is why witchcraft in any age and place changes its apparent form, yet remains essentially what it always has been: the uncanny presence of the Other.
Its eldritch Fire is expressed through our lives, and you can see it shining in the eyes of the witch.