This is not true. Assertiveness Training is not about changing who you are, but rather about teaching you how to communicate more effectively. Assertive people know themselves well and understand where their boundaries lie and are simply able to communicate these clearly to others.
2. Assertiveness is just another kind of aggression.
Assertive behaviour is characterised by one's ability to not become angry, aggressive, overly defensive etc. when dealing with issues. While aggressive individuals may shout, swear, intimidate and display hostile body language, an assertive individual would remain calm and react to the above behaviour by rescheduling the appointment to a time when both parties are thinking with cool and level heads. (Read more about Assertive vs. Aggressive behaviour.)
3. I shouldn't have to be assertive with my friends etc.; they should know how I feel!
Oh if only life were so simple… Unfortunately no one's telepathic, not even our closest friends or relatives, so for them to know how we feel we've got to actually open our mouths and tell them, or chances are they'll never know. Simple as that.
4. People will start to think I'm rude and/or bossy if I suddenly become assertive.
As mentioned above Assertiveness Training is not about turning you into a workplace bully, but rather about teaching you a more effective means of communication. Learning assertive behaviour benefits not only those who have suffered in silence, unable to speak up for themselves, but also those in positions of power who wish to lead a team without becoming completely autocratic.