Regardless of where you are right now in the separation and divorce process, we recommend an assertive approach (in contrast to an aggressive or passive approach) in dealing with the potential splitting that may already have begun. …An assertive approach involves actively learning about personality problems, cultivating energy for dealing with such problems, documenting events (what happened and what was said), and actively presenting your information to legal professionals, the court, or both.

It’s perfectly understandable and normal to feel like responding aggressively when someone acts aggressively toward you. You might try to eliminate your partner from your life and from your children’s lives, or trash her the way she trashed you, but this common mistake backfires in court. Legal professionals may view you as the splitter and an equal party (or the primary party!) engaged in misbehavior. Even if that isn’t true, you don’t want to give your partner any ammunition to use against you in out of court. An aggressive approach by you can increase your partner’s unwanted behavior. Resist the urge to act aggressively, and mentally prepare yourself; in the long run you will be very glad you did.

A passive approach, the next most common mistake, is equally problematic. While it may be tempting to give up or give in on some or all of the issues in the divorce to avoid conflict, we don’t recommend it. Just when you think you have given up enough that the partner with borderline personality or narcissistic personality traits should be satisfied, he may demand even more concessions. If you don’t correct false statements about yourself, these statements may follow you into other parts of your life and possibly create future legal problems. You don’t want to allow your partner to push you around, make false statements about you, and persuade others that you should be punished and restricted by the court.

If you’re a classic avoider of conflict, changing the way you meekly respond to blame and criticism may be difficult—but you must. Court professionals don’t have much time to make assessments, and first impressions really count. If you don’t bring things up, it will be as if they never existed. Being passive didn’t work during the marriage, and it doubly won’t work now.

excerpt from Splitting: Protecting Yourself While Divorcing Someone with Borderline or Narcissistic Personality Disorder by Bill Eddy LCSW, JD, and Randi Kreger