In life I have seen being a passive communicator means getting walked over by everybody.When you dont have the guts to speak your mind you often find that your needs and wants , your thoughts & opinions are brushed aside by so many who are little more aggresive than you.So developing assertiveness as a personality trait would be a good thing to do .
Assertiveness & Aggresiveness we often mix up these two , getting aggressive when you should be assertive.I would say assertiveness is a peaceful way of putting your point accross n aggressiveness is when violence is used to get your point across.Assertiveness is a developed personality trait where you clearly speak your mind & assert yourself ,which is linked to self esteem.It means you do not allow an aggresive person to push you around but put personal boundaries so that aggresive folks do not cross that.Apart from the fact that you feel good about yourself, you tell others how you want to be treated.
Being assertive, I have noticed I am able to express what I think , my thoughts & feelings.I am aware of what is right for me & though I do get angry I do not allow anger to get in the way of my thoughts or cloud them & affect the way I behave.Apart from that I can see & guage what the person I am dealing with is thinking about.Assertiveness is like i mentioned earlier different from aggressiveness in the sense it does not border on dominance.An assertive person unlike an aggressive person does not impose his thoughts on another.More often aggresiveness borders on anger too.
Having mentioned the difference between the two I would like to to highlight that in life being assertive helps in many ways as we generally come across people wanting to dominate you.Be it in relationships, work place or basically everywhere.Assertiveness teaches you to make people respect you as a thinking human, to draw invisible boundaries that they cannot cross.It makes you stand up for yourself & will teach you to say no to what you dont believe in.It gives you quiet confidence in yourself.So as a positive personality trait it would definitely work to ones advantage to learn to be assertive 
