Assertive vs. passive behavior
If your style is passive, you may seem to be shy or easygoing. You routinely say things such as, "I'll just go with whatever the group decides." You avoid all conflict. Why's that a problem? Because the message you're sending is that your thoughts and feelings aren't as important as other people's. In essence, you're giving others the license to disregard your wants and needs. Consider this example: You agree when a colleague asks you to take over a project even though your plate is full and the extra works means you'll have to put in overtime and miss your daughter's soccer game.

You may tell yourself that behaving passively simply keeps the peace and prevents conflicts. But what it really does is get in the way of authentic relationships. And worse, it may cause you internal conflict because your needs and those of your family always come second. This internal conflict may lead to:

Stress
Resentment
Seething anger
Feelings of victimization
Desire to exact revenge

Spot on ....

Thank you for the link !