I have border line split personality disorder, is this easy to treat?

Confusing diagnosis: There is no "border line split personality." there is borderline personality disorder, most often diagnosed in women, schizophrenia, and dissociative identity disorder, both psychotic conditions. It sounds as if you may shift moods/emotional states in a compete way, suggesting strong dissociative tendencies. You need good psychodynamic psychotherapy over an extended time. It's not easy to treat.

Borderline : Get an evaluation from a psychiatrist to help identify what borderline/split personality disorder means to you and whatever else may be bothering you. Consider recommendations for medication if any are given. Get a referral for a reputable psychotherapist to speak with. Meds and therapy combined are most optimal; no just one or the other.