hi Lupita
Someone will come with a more experienced outlook than mine, but here goes...
I say assertiveness is when you stand your ground in a nice way for what you believe, and one usually follows the boundaries one has already set. "Aggressiveness is 'angry assertiveness"... IMO
Without boundaries, keeping people out of our personal space, we can be walked all over and then hate ourselves afterward.
My big one was when a woman at work grabbed my wheelchair, said it was her time with John in the Office and dragged me across the corridor and outside, then went back into the building.
My wheelchair is part of me. She touched me without asking!
What she did was unkind, as though I were not human, but a "mutt who wandered in from the street".
I came home and sent her an email, CCd the Treasurer, John. who witnessed this, and to the President.
I said that I could have her charged with assault for that. (& Battery would be if she hit me) That my chair was a part of me and I would see to my moving about, that I doubted she would take a walking person by the arm and physically drag them across the corridor and outside.--(One boundary mentioned that is wrong is touching a person without his/her permission.)
Nothing came of it. I had spoken my piece, yet another time, my chair was angled in front of a desk drawer and she said, "I will just move you over a bit". I said, "No you won't. I will move myself!" and I did... so she could access the drawer. (With a walking person she would likely have asked them to step over a bit..IMO) I had 'leveled her with a look" at this point and although I have received no apology from her, I hear she is 'afraid of me'.
I doubt she really understands what she did, but I stood up for myself and I felt good.
Does that make sense?
There were no raised voices, no anger, just statements and mine were to assert my position, my boundaries, on her actions.
xx
Izzy
EDIT] My feeling is that if I had returned to the building to be assertive, it would appear to be more confrontational, as though I were looking for a fight, so I left it to email