Recently I have become convinced that my sense of self is unreal.
The first reason this happened is because of an argument. We have our sense of identity when waking, but when we dream, we seem to be variations of ourselves, or even different people entirely. The only thing which unifies the various people we are when waking and when dreaming is the perspective, or the personal horizon, or the raw ability to experience, which contains the senses of identity, memories, thoughts, and so on. Your subjectivity, at its most fundamental, is independent of everything else you perceive yourself to be, because it is prior to all of that, and necessarily so.
The second reason is because I experienced the detachment between identity and awareness. Several times, actually. It starts with my hands feeling oddly heavy. Next I lose feeling in my legs, then my chest. My head starts feeling very heavy. I then feel a strong sense of vertigo, like gravity is changing direction, and finally, a sense of something breaking. At this point everything being reported by my senses seems to be a projection onto a movie screen, not something I identify with myself. I then turn my attention inwards, and have the sense of seeing the back of my own eyeball, in a way - I notice the origins of my own thoughts, seeing them as external things. Finally, all experience (including the experience of thinking) detaches, leaving me with awareness of my own awareness and nothing else. Eventually, I randomly snap back into my body, sometimes losing a bit of time without any memories from the gap.
Are Buddhists or Hindus right about the self? I'm not sure. I definitely don't experience any grand unifying oneness with Brahman or supernatural insight during these episodes (though using the words "I" and "experience" in this context doesn't seem right). I've had a couple episodes where a vestigial part of me felt like it could move "sideways" and slip into the sense-identity-experience of someone else, but when fully myself this seems like schizo nonsense.
On a side note, I have had a very hard time telling the difference between my dreams and my memories lately. I have to think about the events that preceded and followed each memory and make sure they make sense, or find a physical record of the event in question. I've also had the experience of a dream-memory-self "bubbling up" from inside me while awake, where the person I was during a remembered dream floated to the top and was superimposed over me for a second. So far I'm still fully functional and (by all appearances) sane but this is a worrying sign.