In regards to souls ... I have never met anyone that I feel this is their first experience. The term 'old soul' has been overused (in my opinion).
There are a couple of books that I really enjoyed reading a few years ago ... Journey of Souls and Destiny of Souls by Michael Newton. The author is a hypnotherapist in California who's practice includes helping people with past lives ... but, more than this ... the lives between the lives, or the spirit lives. Very interesting.
When thinking of an old soul ... you have to think of this ... we have not only incarnated in this space of earth but have been in many other places and spaces. We are travelers of experiences of what it takes for our souls to grow and evolve, which is constant. Earth is young ... so look at the age of the earth and go beyond that to the age of the Universe and that is how long we have been around.
I have found personally that when we focus on today and what this day holds and how it impacts our lives ... our tomorrows follow suite ... and our yesterdays hold true.
Peace to you, Tami
