Why would I do something like that?

[someonewholovesthemselves]

I shouted at my sister, i have C-PTSD. Our father is a narcissist. My trauma does not justify my behaviour. I did not do it voluntarily though. I remember doing it vaguely. I am hurt that I hurt her. I am moving to a separate area in the house to protect myself from him and to protect them from my outbursts. I love her alot. I feel heartbroken that I did that. I don't know what to do. Any suggestions would be helpful

[Chart]

SWLT,
Without more details it's difficult to say exactly, but here are some thoughts.

Your own behavior is probably modeled on your attachment figures (parents). I am guessing that people in your family often communicate by anger and shouting. I agree with you that this is inappropriate. That being said it's nonetheless very hard to change our behavior once it is a learned part of ourselves.

So I suggest that you first forgive yourself. Try to understand beyond the guilt you feel. You are struggling. First forgive yourself...

Second, talk with your sister and apologize. Ask her forgiveness and try being open and honest (if this is safe to do).

Already, if you can do those two things well done. It's a great start.

Sending support and hugs. (Wish I could write more but I'm at work
 

[someonewholovesthemselves]

When you said, "Sending you support and hugs. Wish I could write more but I am at work"
You made me laugh. It has been a long time since I have genuinely laughed.
Thanks

[Chart]

And you'll never guess the work I'm doing Never in a million years! I'm scraping the moss off an old clay-tile roof... I hope that brings another laugh. Sure makes me chuckle 🤭

Yeah, good advice Swlt, let's try to laugh if we can. I can sure use it!
  

[Armee]

There's a lot of power in just acknowledging directly the remorse to your sister. Taking ownership for behavior helps. I totally understand not even feeling like you said it. I have "parts" pop out too and say things for me without my consent...hearing them being said as I say them with no warning ahead of time and feeling shocked about it.

Still just taking responsibility for having said it and apologizing can be super powerful especially since your sister is also growing up in a narc family and narcs never take ownership for their behavior.

I'm sorry you are still living with them. That's really really tough.

Quick edit to add: You do not need to reply.

[Aphotic]

As the others have suggested, please forgive yourself, and perhaps apologise to your sister if you are comfortable doing so (but it's been a while so you may have already done so)! Apologies go a long way, for other's sake and your own.

I resonate with your worries though. Sometimes certain things seem to come out of nowhere and we come to trying to comprehend - "Why!?". I am no professional but I think sometimes when our brain isn't too sure of what to do, it'll take just about anything it can remember from our various authoritative figures. However, you are of course not them, and you have the awareness to recognise your actions which is so incredibly meaningful. This awareness alone is a powerful tool and I am hopeful that you will be able to wield it for the future as well.

I also commend you for not shifting the blame, it is inspiring to me.
Wishing you well.

Regards,
Aphotic.

[Little2Nothing]

The fact that you can feel remorse for what you said says a lot about who you are. 

You obviously have a compassionate heart. Even if your sister rebuffs your apology, I believe deep inside she will be touched by your humility and genuine sorrow. 

Saying things and doing things that we ordinarily wouldn't say or do is part of the trauma you endured. It will get better. 

I have been trying to pause when I feel strong unwanted emotions, before I respond. Though I am not nearly as successful as I would like. I apologize a lot.