They can express what they feel. They confidently share their opinion. They can say no without feeling guilty. They unapologetically say what is fair even when it is in someone else's favor. They can disagree with people respectfully. assertiveness is a personality trait that allows someone to take charge of their own life and the lives of others. It is a personality trait that allows someone to be strong and assertive when they need to be, and to stand up for what they believe in. It is a personality trait that allows someone to be confident in themselves and their abilities, and to be able to communicate their feelings and ideas clearly and confidently.