I have always been an assertive person, so, I cannot speak from the other side. I think its something that is in you; kinda like being a good singer, a talented artist, or something along those lines. Some people have that natural magnetic personality, are natural leaders, and some arent. But, I think being assertive, and being a leader, CAN be mutually exclusive; you dont have to be one, to be the other. A leader can recognize strengths and weaknesses in others, and employ those to the benefit of all, fr instance. Assertiveness is a little different, in that, essentially, you are strong willed. A good leader CAN posess this trait, but doesnt necessarily have to. Hope this all makes some sort of sense!