I just picked up Eckhart Tolle's book "A New Earth" which I am still reading. It's not a fast read, you have to digest it all and try to internalize it.
I don't have to type this out now, but Chapter 5 is "The Pain Body" and it's about how we are trapped in the voice of our head, which is conditioned by our past, and therefore most of the time it's impossible for us to simply be in the present, in the pleasure and joy of a moment. I can't really paraphrase it well, just turn to page 129 and start reading! "The Pain Body."