Do you know someone who is overly aggressive or too pushy? That car salesman who approached you before you even got out of your car? Did he come too strong or too fast? You probably get turned off with that. Being aggressive or overly aggressive has its own time and place.
On the other hand, we must be assertive at times. In business, assertiveness is an important quality. Being assertive does not imply that you are overly aggressive. Even the most soft-spoken, mild-mannered people have to be assertive sometimes. Being assertive is expressing yourself to show the value in whatever it is your promoting.