This is where universal unconditional love comes from. For most of us, we recognize that we can still have a positive relationship with someone even if they make mistakes or occasionally hurt us – because chances are, they really didn’t mean to cause harm.
Narcissists don’t possess the capacity for object constancy. Therefore, when it comes to the broadly known ‘devalue and discard’ phases, they feel such dislike for you, they have no problem treating you with cold indifference and loathing.
The narcissist understands that you, on the other hand, have object constancy and they’re keen on exploiting this trait.
The narcissist knows you’ll stick around through all the abuse because you’ve experienced their good side and how well they can treat you – when they believe you deserve it, of course.
But this “good side” is all a façade and part of the cycle to keep you hooked and begging for that next fix. In fact, when the narcissist is being kind, it’s an integrated part of the abuse.
https://www.linkedin.com/pulse/cycle-narcissism-why-do-teeter-between-love-hate-kim-saeed/