I suffered from derealization for years, in fact for a time it was worse than the anxiety itself. I thought I would live with it forever but at some point it just slowly dissipated and went away. There were certain things that used to trigger it, like bright fluorescent lights. I don't think I have experienced it at any point in the last 2 or 3 years. I wish there was some kind of advice I could give you but it just seemed to go away on its own.
Everybody knows you only live a day but it's brilliant anyway