Assertiveness training has been used with shy, anxious, depressed, stressed, aggressive and other kinds of persons. So it may be wise for married couples or friends or work groups to take assertiveness training together, emphasizing cooperation and congeniality. All the research observations referred to in the last paragraph apply to formal training provided by graduate students or professionals. There is almost no data about the effectiveness of reading about assertiveness on one's own and practicing with a friend. As we change, we should be alert to the possibility of making life worse for others.
Much research is needed.
For the extremes, they recommend psychotherapy. Likewise, if the people around you will react hostilely to your being graciously assertive, perhaps you should see a lawyer. Refusing to make the coffee may result in losing your job or a promotion, so move cautiously. It may be wise to postpone a confrontation until the time is right. There is no known danger, although some research has suggested that certain men believe that sexual aggression, such as kissing, fondling, and even intercourse, is a little more justified, if the women has initiated the date, gone to the male's apartment, let the man pay for everything, etc.