Losing yourself to appease the narcissist - my experience
Anyone who has tried to love a narcissist finds out eventually that their nervous system can't handle the hurt that comes with the way they relate to you. The narcissist can't love. Not in the way we know or feel. I never quite understood what it meant that a narcissist sees people as extensions of themselves. I think it's not quite right. An extension implies they kind of think others are attached to them or part of them. Maybe like puppets, or an appendage like their own finger that they can control. But it's not that. It's that they can only see a person as an object that either supports their ego or absorbs their shame. Those are the only options. Like you become an external component of their fragile identity and sense of self.
So you learn exactly what to do to fuel their narcissism, find ways to appeal to their ego, and keep them positively engaged some way or another. Because it's the closest thing to love you might get from them. And at least you're not being attacked. But you are. Your own sense of self is under attack as your own feelings and ambitions are neglected. You learn to neglect yourself when you're with the narcissist because it feels safer and easier. But it's not safer. You might feel like you're protecting yourself from being devalued by them, but all you've achieved is devaluing yourself before they can. You walk a constant tightrope between protecting yourself and losing yourself, to maintain their fragile sense of self at the expense of your own. So you can fly under their radar and avoid the attack. But the attack is on yourself. And your nervous system responds either way.
[Edited to remove gendered language]