To have a successful relationship with a narcissist? Granted, a relationship is possible with anyone with any given traits but I mean a truly successful, long lasting, free of infidelity relationship?

I was diagnosed bipolar and take medicine regularly which has helped tremendously. I was previously in a relationship with another bipolar (rapid cycling) which did NOT work out. Months after my ex that I was with for 5 years and had not spoken to in 5 years suddenly resurfaced with claims of having always missed me and still having feelings. She is not diagnosed NPD but she fits a lot of the qualifications. I realize I am also co-dependent but is it worth it to reopen this chapter and have it be a successful relationship or should i head in the other direction?