The adult children of narcissistic parents are attuned to the needs and expectations of self-absorbed people because this is how they survived childhood. They learned that to be accepted (if not truly loved for who they are), they must shape their behavior/personality to meet the needs of others. As adults, they naturally fall into the same pattern with other narcissistic people because it is familiar to them. They believe such self-abnegating behavior will earn them love and acceptance. Each new relationship revives the hope that this time, at long last, someone will give them the love and full acceptance they have always longed for.
For this reason, the adult children of narcissistic parents need to be aware of the ways they will sacrifice their own needs to serve other selfish people; they need to place a value on their own needs and develop a sense of self-worth apart from the approval they constantly seek from their partners, friends, colleagues, etc.