When Your Partner's Ex Won't Let Go- Survival Strategy

[NYLilac]

Are you now or have you ever been in a relationship with someone whose obsessive ex-spouse/ex-partner couldn't accept that it was over months, even years after the breakup/divorce and actively tried to sabotage their subsequent relationships? Were you and your significant other able to overcome this difficulty? Why or why not? If not, what would you have done differently in retrospect?
The input of all MBTI types is welcome.