Others' anxiety, or sadness, or fear, becomes my own. Then, when I can't fix things for people, I torture myself inside for being useless and ineffective.
This is pretty common with empaths or highly sensitive people, they can easily get overwhelmed and take on other people's emotions or emotional baggage. It's quite opposite with aggressive personalities who actively try to dump their emotional responsibility onto others.
There's many different strategies for a potential Empath or HSP (Highly Sensitive Person) to deal with the dangers of taking on other's emotions. Typically it's some form of boundary setting and learning how to identify emotions.
I like Karla McLaren's work the best, she really can translate and teach the language of emotions for others. Elaine Aron might be one of the earliest pioneers who dubbed the term HSP (Highly Sensitive Person) and estimates 15-20% of the population is HSP. Rose Rostetree is more metaphysical/new-agey has developed techniques for empath empowerment and energetic literacy, has also written several books.
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Within a trauma and PTSD context. I think some people develop and refine empathy skills due to adapting and trying to survive in an extended overwhelming and disorienting traumatic environment.
In order to avoid or prevent dangers and outbursts from the abuser, we learned to pay attention and be sensitive to their emotions. Learning to predict when they might blow up, meant a little bit of a head start to run away or defend ourselves. Also learning how to soothe, take on, and care for their emotions, also would help our safety, because it lowers the chance of them getting triggered and taking it out on us.
This becomes a habitual pattern, which might be the foundation for codependence, where personal identity gets replaced with a care-taking (outer prioritized focused) identity, with an unfortunate byproduct of losing touch with our inner self, personal needs and emotions.