I think that this definition of assertiveness is quite accurate.
"Demonstrating assertiveness means there's no question where you stand, no matter the topic. Cognitively, to be assertive implies a lack of anxious thoughts in light of stress. Behaviorally, assertiveness is all about asking for what you want in a manner that respects others. Assertive people don't shy away from defending their points of view or goals, or from trying to influence others. In terms of affect, assertiveness means reacting to positive and negative emotions without aggression or resorting to passivity."
The part in bold is what is referred to in the Dirty Dozen, as in the examples given by Mr.newfy.