Assertiveness, what's that? Oh you mean when I hold in my anger for so long that it comes out as, "bleep off," or "bleep that," or "bleep you!". Oh, you don't mean that?
Oh, you mean I just hold in the anger and stonewall the person I am mad at? Oh, I can do that! Isn't that better than "bleep off"? I don't have any idea what you are talking about with assertiveness. I grew up in a home where it was one way or the other. It was violent or silent. Black and white are what I lived. There was no grey, so I have no idea how to be assertive.
Chances are very good that while I am trying to sort out assertiveness, I might tell you to bleep off a number of times. Not to mention the guilt that comes with standing up for myself. After all... standing up for myself usually led to a whole bunch more trouble in my family.
It wasn't worth it.
Isn't it better just to avoid the person? This way I won't tell them to bleep off and I don't have to feel angry inside when I am around them and they keep doing things I don't like.
Assertiveness.
Saying what you feel about another person's behaviour and what you would like differently. When you don't clean the dishes, I feel frustrated and I would like you to do them tonight.
Sticking to the facts about what you see, hear, observe the other person doing not what you think they are thinking or feeling or why they do something you don't like.
Being clear about what you what and offering a solution to get it.
Setting a boundary between what is ok and what is not ok for you.
Advocating for yourself in a kind way.
Asking yourself, "how can I ask for what I want with dignity and self-respect?".