Monkeydust I will try to explain how dp can work as a defense mechanism. It is not a pleasant way to feel even though the mind is protecting you. I know it certainly does not feel like it is but from what I understand in my case this is part of it.
One day a few years ago I lost a few very dear friends of mine in a terrible car accident. I was totally devastated. At the time this happened I was suffering from an illness which was also very painful and I was very ill. I tried so hard to keep it together and then one day I could no longer feel like I used to. I felt like I was floating away, felt removed from everything. Felt numb not there. I knew I was terrified but could not feel the terror. I ended up in hospital for many months and spoke very few words. I went into a world of my own. The doctors told me that I was suffering from depersonalization and some day I would come out of it, they said the shock was to much for my brain so I simply walked away in my mind. I hope this helps a little bit to understand how the brain can work. It is not a pleasant way to block something because it feel worse than the actual trauma I sometimes wonder, but I have been trying hard to deal with all of this. As I started to try to heal it happened again another loss, many lossess in a short time due to illness and the accident. My mind could not handle all of this pain so it took a time out. I will keep fighting to get well, it is a long hard struggle but I have been able to accomplish alot in my life even though my pain is still buried deep within. The dp is not going away and the doctors say that the brain has not yet been able to deal with the pain, hopefully I will heal in time, I will always keep trying because life is precious and I want to be well again. Hope this helps you understand a bit better.