The most potent weapon you have against a #narcissist is #selfRegulation.
Narcissists use #emotions to manipulate you. And a lifetime of doing this made them incredibly adept at this. They will analyse you and figure out which emotional strings they need to pull to play you like an instrument. You'll increasingly loose yourself in increasingly desperate attempts to get on their good side. To get back that person they were in the beginning. Neurologically speaking it's literally an addiction (look up #traumaBond if you don't believe me).
Good self-regulation practices will allow you to become immune to their manipulation. For this you need to become centered in yourself. Which means: you need to face your own #trauma.
However if you manage to do that, then you'll become stronger than you could have ever imagined. Your narc gives you nightmares and makes you feel powerless? You'll begin to see them as a toddler throwing a fit (which is surprisingly accurate, psychologically speaking).