Meditation exercise (consult a doctor first if you have PTSD): Try to remember every person in your life who ever did you harm.
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Every time a friend or lover let you down; every time someone humiliated or hurt you for personal gain. See if it still hurts afterwards.
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A lot of "trauma" is just squeamishness. Humans are remarkably resilient. If you reallly can't do it... surprise: you won't manage to try.