“Do no harm” is a phrase that has been around for a very long time. I think this is a good concept to live by, up to a point.
I read somewhere (I do not remember where) an addition to this phrase that I really like: “Do no harm, and do not let anyone harm you.”
When we are aggressive, we harm others. When we are passive, we let others harm us. When we are assertive, we find the balance. We do not harm others, and we do not let others harm us.
For more information and exercises to help you become more assertive, or assertive more consistently, see my book, Don’t Act Like Prey! available through www.SusanLFarrell.com or from Amazon.