We are not drawn to narcissists, we are drawn to people who we believe we can help, because it's in our nature to (need) to help, not that we are selfless, we are doing it for ourselves, and by helping someone who needs our help, we are helping ourselves, which gives us the motivation we need in our lives. 

Narcissists are drawn to people who want to help them (how they are labeled as takers), their quest is to find someone who can help motivate them in their lives.

The reason why these relationships always fail, even though our brain tells us that we need each other, is because of lack of introspection, we strive to FEEL, and in just feeling all the time, a part that we enjoy -and we should enjoy our feelings (emotions), our brain rewards us for experiencing them- we do not give ourselves time to examine our emotions, so we are stuck in a loop of feelings, without moving forward, which is what we actually want to do for ourselves, we want to help ourselves, but we need to do it consciously, otherwise we crash and burn. Introspection (examining our emotions a d the thoughts and events that evoke ' or trigger' them, enables us to get out of the feeling loop, and move us forward into helping ourselves and the other person in their life quest of self fulfillment.