Yoko's pretty much covered it, but I'll say this.
We stand on the shoulders of our trainers and masters in spirit. The lessons and knowledge they give us, we in turn not only pass to others but expand upon through another lives lessons and experiences.
I want you to think about how many "Ghost" you see every day.
Memories associated with people to the right words or actions.
When you use that technique, and I'm sure you have one, that your master hammered into your head, can you not hear his voice?
I know I do with my right cross. "Keep your elbow in Jess.. alright fix your shoulder and that's perfect.... ok now one more good one."
I can hear it clear as day.
Its with everyone, even people who still live. The lesson they taught you instill a part of them in your mind.