I think of "an it harm none" and other variations of that as a sort of guideline to the idea of striving to do good with your life. In truth nature, God or whatever works equally destructively and creatively to form reality, without the concept of "good" and "bad." Whether you do good or bad in your life, the cycles will continue and for every great push one way, eventually the scale will tip the other.
The idea of "harm none" is in awareness of your actions; there will never be an action that has no "consequence", but the benefits can often outweigh consequences so they are worth the sacrifice. It's both action and perception. By taking action you are sure to cause harm, but by taking no action you are not benefiting anything either - so if you must take action, be aware of your actions and strive to create as much harmony as you can with as little harm as necessary. Perception comes into play in realizing that "necessary harm" in itself is not always "evil". Sometimes the worst possible thing that can happen to a person can be nothing more than an experience if it is used to build something stronger.
So "harm none" is not just an effort to just not do anything to hurt or upset anyone, it is a way of living so that you can reflect on your actions without guilt or shame. When you reach a point in your life when you can look back and see that every small event was a necessary action to lead to exactly where you are now; and if where you are now is a place that has created a good that outweighs the bad, then that is a life where you have, in a sense, harmed none.