That's an interesting question. You are you, that's a fact. However you have a perception of mind that it you are attached to, and that perception constantly tries to look for you.... it's a bit like pointing at your own face and saying "this is me" but then you can't actually see yourself. The observer cannot observer the observer because it already is the observer. As such the mind may perceive something 'other' as though it is the "I"/"you" and associate and become attached to that thing, and then feel a sense of disassociation; simply because of it's knowledge that if it can observe "you" elsewhere then it must somehow be separate from the Self. These perceptions can manifest in various ways, including different personalities, or just different moods or even physical sensations etc. So, yes you can have a 'sense' disassociation, though the reality is that you are not really disassociated from yourself. By working to let go of the 'other' we can come back to being our true Self.