I hurt myself deeply, though at the time I had no idea how...

I hurt myself deeply, though at the time I had no idea how deeply. I should have learned many things from that experience, but when I look back on it, all I gained was one single, undeniable fact. That ultimately I am a person who can do evil. I never consciously tried to hurt anyone, yet good intentions notwithstanding, when necessity demanded, I could become completely self-centred, even cruel. I was the kind of person who could, using some plausible excuse, inflict on a person I cared for a wound that would never heal.