Once you realize that a narcissist is pushing you around, you need to learn how to defend yourself.
You don't have to put up with the manipulation, gaslighting, embellished half-truths, and outright lies.
With the right approach, you can frighten a narcissist and enforce boundaries.
Although they always seem to have a comeback that makes you look unreasonable, they are not invulnerable.
You probably can't improve them as human beings, but you might succeed in getting a narcissist to do what you want — which can range from pulling their weight to leaving you alone.