Dave Pollard's Effortlessly and Unintentionally Causing Pain to Others really hits home on some of my own life lessons.
To begin with,I am not responsible for how others feel. This principle is about setting good ego boundaries -- it is not about being callous towards how they feel. It stems from the principle that "others are not responsible for how I feel" being carried to it's logical conclusion. Not having others responsible for how I feel is surprisingly very empowering. It gives me the freedom to stop and recognize my feelings, to choose how I want to feel and to react appropriately for the situation. This then leads to better recognition when others are attempting to manipulate my emotional state, and, when I'm unintentionally trying to manipulate their's. This principle means that I am no longer being swept along by external forces, but by my own guiding light. My responsibility is in being aware of, but not responsible for, how others feel.
Although this has been a long-guiding principle, it was particularly important when interacting with one person in my life. This person had such a distorted frame of reference that I could never foresee and avoid hurting them. Neither one of us was "wrong", but the hurt couldn't be avoided because the triggers didn't make sense from my frame of reference. This "not making sense" leads to the next principle.
Next, I should strive to deliberately not hurt someone. It might be a situation outside of my experiences. Being deliberate means that it is my responsibility to learn why and how it hurt the other person so that I can foresee and change my future behavior. Unfortunately, if the injured person doesn't communicate immediately (to correlate facial expressions and subtle verbal remarks) how the incident made them feel, then the learning process will never complete.
Finally, contributing factors also play a part in increasing the potential for and the severity of the pain others experience. These factors are indirectly caused by the structure and mobility of modern civilization. Namely, hierarchical structures and easily changed peer groups are systemically different from how humans evolved: respect-based meritocracy and small family groups.
Hierarchical power structures: boss-employee, teacher-student, parent-child, will often have "interaction decisions" (decisions that should be resolved by consensus) made unilaterally by the person higher in the hierarchy. The person lower in the hierarchy is walked all over, even if the resulting hurt was unintentional.
Mobile peer groups also add a subtle difficulty to human relationships: the loss of shared experiences. Situations that would normally be known to avoid, maybe talking about a loved one that has died - but not known, cannot be avoided without additional communication which most people are quite poor at engaging in, too.
In conclusion, I agree with Dave that our experiences with other people often have one or another person unintentionally getting hurt. I would add that by being aware of the systemic problems of hierarchy and mobility, and, living our lives with good ego boundaries and awareness of other's feelings, most potentially hurtful situations can be avoided and worked through.