CONSCIOUSNESS HAS MANY COMPONENTS.
When I was first trying numerous meds to find the one that worked best for me, one of them removed a significant portion of my "Self". The scary part was that it also removed access to any memory of this portion of me ever existing at all. Thus part of me disappeared yet what was left of me was completely unaware of this. It was not until I got off this drug that I said OMG since now that it had returned it was clear that such a part of me was a very important part of me indeed.
Just imagine if someone stole your car and also gave you a drug that removed all memories of you ever having a car, and then kept this approach up until you had nothing left at all. Meanwhile, from your point of view, you have lost nothing at all. The perfect crime. Freaky !