"Everybody has to be assertive, not aggressive.
Those two words are totally different.
You can be assertive and very humble.
You cannot be humble and aggressive.
Aggressive is trespassing somebody else's right.
Assertion is simply making your right proclaimed, clear.
These are totally different processes. Assertion is everybody's fundamental right: "If you are not capable of understanding then I have to shout, but I am not interfering in any way in your life. I am simply saying, please keep away from my territorial prerogative.
I will never trespass your territory, but the same I expect from you.
That's what I would like our small children to be from the very beginning -- assertive, not aggressive; humble, but not ready to be enslaved by anybody."
Osho, excerpted from From Misery to Enlightenment