You allow others to make the choices. Since you do not indicate what you want, your goals are not achieved. Others achieve their goals at your expense. You can become a storehouse of pent-up anger that when you reach your limits can explode into violent behavior. In contrast to these two extremes, assertive methods emphasize firmness, not attack.
Assertiveness is a direct, honest expression of feelings and desires.
Like aggressive behavior, assertive behavior acts in your own best interests, usually achieving your goals. However, you also respect the rights of others. While you maintain your self-respect, you allow others to express their feelings, and you respect their needs. In this way, others also achieve their goals, and their feelings of self-worth are maintained. In addition, when you have the decision-making power, you are modeling a respect for others.