TW: self harm

One if the most insidious things about BPD for me is anger. I don’t know why anger, but I struggle to restrain myself from throwing a violent temper tantrum when I’m angry in public, and in private I turn into a fucking monster.
It is uncontrollable rage, half the time I can’t even speak i’m so angry, and having no words to express this anger makes me even angrier and I want to punch walls, i want to scream, i want to tear my arms open again. It feels like a monster inside of me that wants to get out and has blood on its mind.
I feel helpless to this. I have hurt people I love because of this. The only coping mechanisms I have found to work in the past are smoking cigarettes or cutting myself, both habits i have fought hard to quit and besides a few relapses I’ve managed to abstain.
But this leaves that anger with nowhere to go. 
Until today when I found that holding my breath for extended periods of time seems to force my body to calm down and then i can think again.
PLEASE BE RESPONSIBLE TRYING THIS!
Obviously I don’t want you to try this and end up passing out. Probably don’t be driving either. Sit down somewhere, or pull over, and hold your breath for as long as you can and then exhale. 
It calms me down instantly.
Hope this helps