BPD that is traumatic in origin comes with a ton of unresolved trauma and all the associated aftermath lurking just beneath the surface, waiting for the faintest trigger to resurface in order to be expressed and hopefully resolved. 

We know this is part of the answer to the perplexing question many people with BPD ask themselves: Why am I constantly overreacting? 

You aren't overreacting, actually. Your reaction might well be out of proportion to the present event but it's likely that this event triggered the pain from the past of the unresolved wounds of which you may not even be aware or have detailed understanding. If this is the case, situations in which you realise you have apparently overreacted are a golden chance to make use of self-reflection skills you're hopefully learning because it can give you great insight about the wounds and the corresponding issues that require your attention. As unpleasant as they are, triggers are extremely valuable. They point the way toward healing and help us with self-awareness.
Don't dismiss your "overreactions" as an awkward personality flaw. 

Keeping this in mind, I had a thought I'd love to discuss with you. 
People with BPD are quite often accussed of "playing the victim". Sometimes others are quick to conclude that this is always "another BPD manipulation trick" but is this true? I think you know the answer. 
Perhaps you've been told to stop playing the victim and that only made you feel worse because you... aren't playing at all. You genuinely feel victimized, helpless, overpowered, betrayed and so on. We know that with BPD, there's always the question of "Am I justified in feeling this emotion or am I overreacting again?"

Well, if you eventually come to realize your feelings of victimization weren't an accurate match to the present and you find yourself slipping into this feeling frequently, then this could very well be one of the unexplored and unhealed wounds from the past. It's quite likely that you are right in feeling like a victim of some form of abuse, it's just that the abuse started and ended years ago, perhaps when you were a child even, and you still haven't come to terms with that traumatic event or even traumatic time and haven't found closure, which is why those feelings keep being triggered today. 

I guess what I'm trying to say is, I hope that you will not allow people to shame you into devaluing and ignoring your own triggered pain just because they don't understand it. Just because your feelings are out of proportion to the present doesn't mean they are out of proportion to your past that still lives inside you through the wounds that you carry. 

The hearts of people with BPD aren't dramatic. They are badly bruised, and that is why the slightest touch sends them in deep pain when a healthy heart wouldn't even notice the touch. 

Don't despise or ignore your triggers. Listen to what they have to say. Let them identify your wounds because the wounds *can* be healed. In fact, they *must* be healed because you deserve it. You deserved help back then when you were a victim of the abuse no one helped you escape and you deserve help now that you feel you can't escape your past. But there is a way out of the dark prison chamber, and what we are tempted to despise as character flaws are usually what can light the way out. 

I wish you all the best on that healing journey to freedom, and I'd love to hear your thoughts and experiences about this.