Is there an effective therapy for borderline personality disorder?

Yes: Dailectic behavior therapy has been used successfully with borderline patients to decrease self harming behaviors, but a long term relationship with a therapist is what it takes to overcome this problem.

DBT: Dbt, or dialetic behavioral therapy, formulated and developed by marsha linehan, pH.D. Is currently though of as being very effective. Just about the biggest goal of this kind of therapy for this kind of disorder is to maintain boundaries.