Only recently has derealisation or depersonalisation been recognised by the mental health profession as a specialised symptom of anxiety. Back in the early 1970s when my anxiety disorder began it was completely unrecognised and unknown. But I now realise that among other symptoms of anxiety I experienced a mild form of derealisation.
I used to describe it as "feeling that I wasn't there" and "like watching everything on a large screen television." At the time I realised it was another symptom of anxiety neurosis ( as anxiety disorder was called then, before that it was called neurosthenia) but it didn't bother me too much, I was more concerned about the other symptoms. And as derealisation was unrecorded and never mentioned anywhere at that time I didn't think about it much and it sort of died of neglect because I didn't pay it much attention. I now realised that I had subconsciouly 'accepted' it and that's why it ceased. I can't even tell you when I stopped feeling it.
My understanding is that derealisation is the minds way of withdrawing us from the unpleasant realities of our anxiety disorder.
I know there are several people on this firum who suffer from derealisation/depersonalisation and I appreciate that mine was a comparitively mild form. But I wanted to record my experience so as to let them know that you can and will recover from this symptom of anxiety, you will be free of it, it is NOT a life sentence. Perhaps it is best treated by attaching less importance to it and trying to accept it for the time being. And when the general anxiety disperses so will derealisation too.