Perhaps the central point is that assertiveness is not about winning and losing. It's only about winning. True assertive behaviour helps everyone to win something, as it removes unhealthy competition, the need for one party to beat another. If you win, they win too. It is possible, with solutions to difficult situations that recognise everyone's needs and wants, and that aim for constructive compromise that gives everyone something.
Assertiveness is about much more than techniques.
Understanding where you are coming from - what situations you can and can't handle at present. Having a sense of self-worth. Helping you to control the way you feel about the world and the people in it rather than the other way around. Recognising your own and other people's rights and responsibilities. Read about Passiveness and Aggressiveness .