I think working through my anger was the key to helping me be able to "lose" my borderline-personality diagnosis. It was done with the help of therapists. I made a list of all the things from my childhood I remembered that I was mad about and ultimately tore it up, burned it, and buried it. And I went through hypnosis and a lot of talk therapy and reparenting. I also went through two DBT bouts.
I still remember how that rage felt sometimes. It was scary even to me. It's so nice to have that gone.