Self assertiveness is the ability to express your feelings constructively and be open to others and yourself about your needs. This leads the way to boost your chances of of getting what you want.

Assertiveness reflects one’s own confidence about an aspect; I mean 100 percent confidence. It has a close link with individual freedom. I am free to express my views which I feel are right; and I find my views agree with reason, which need no specific evidence. At the same time I do not ignore another person’s views or freedom, but do not explicitly accept them either. No aggression; only peace. It is an essential quality but we should use the right words at right time. Otherwise it may hurt others, because words have power and feelings. Assertiveness is the gentlest way of expressing individual views, without causing damage to the leaf and the thorn.  

. Assertive people use their reason and logic as the tools for convincing the people. It is the way of expression used by assertive people with out using agression

Very true, but sometimes rude words are part of the book when a person is absolutely dumb or trying to ignore the rules. You see the soldiers use their guns when they have no options left. 

Agreed. Using a suitable way to deal with people is the best solution. Then it is the trait of people blessed with self assertion. Coax, cajole, or use that language that's understood by the other party