It is my belief that people do indeed live many times, many lives.
Some were wonderful happy lives, others more painful and difficult.
I am also of the belief that at some level we retain all memories of these lives.
Memories of these lives or glimpses of certain bits of them are triggered by everyday life, giving one a certain feeling of being someplace before(when you have never been) or feeling recognition of a person(who you have never seen before).
Dream recall is very common, as is remembering from a meditive state.

I also believe we can carry the memories of hurts and injuries we suffered in previous lives. Our cellular memory holds onto these things and can produce actual problems for us in this life.
There are many books on the shelves already written about this phenomenen, documenting many cases. I refer you to read the works of Brian Weiss and Michael Newton as two excellent examples.

I would write some more, but my time here is up today, so I will leave it at this short piece. sunshine