The power of this introspective moment of insight has an interesting parallel with the similar concept of catharsis. However, catharsis is outward focussed. It is through the careful absorption of art (e.g. a stage play in antiquity), which is fiction, and divorced from the self, that a healing release may occur.
So for the neurotics trying to avoid the trap you described, try channel that curiosity outward, direct it towards the minds of others, by paying careful attention to fiction. It won't change behavior per se, but at least will help with stepping out of oneself.
GP gives a hint:
> You haven't changed your behaviour at all.
TLP[1] said it best:
> There you go again, thinking about yourself. Your impulse wasn't to say, "am I doing this to my kids?" or "how will I act differently?" It was to wonder about your own nature.
1: https://thelastpsychiatrist.com/2012/10/the_story_of_narciss...
Although, this does fit quite well too: "I don't want to be with someone who doesn't care to drink tap water."
Anyway, not saying you said it was the same as the DSM definition, just adding some perspective since I read a lot of TLP and naturally compared what I read in the OP to what I remember from TLP's blog.
This is what I'm going through with my partner right now. She went through a program that made her really evaluate her past and behavior. After the year program she thinks she is "fixed" and everyone else needs to live their life according to how she thinks is best.
It seems like an impossibility for her to even change 5%. If I could even get her to accept that she has a mental health problem that she needs to face.
People with narcissistic traits can work towards undoing the damage done to them; but, once you're at the level of a personality disorder it becomes more about coping with the inevitable and continuous fallout. Genetics, trauma, and childhood abuse all come together to create a shell of a human being who, motivated by self-preservation, exists only to consume, exhaust, and expel other human beings.
There are no evidenced treatments, and there is no saving them. They are not capable of changing -- if they were, they wouldn't be (by definition) narcissists. The best thing we can do is teach people to identify and protect themselves from these lost souls.
People can't tell you how to stop being a narcissist. If someone tells you exactly what to do, you'll do that thing, and then stop. "I'm doing that thing now, so I'm not a narcissist!"
Your mind will simulate the most awful pain imaginable just to protect against changing your behaviour. You think your suffering is making you a good person, that by looking at the painful parts of your mind you are no longer a narcissist, but you're at the same place as you were before. You haven't changed your behaviour at all.