The ability to negotiate successfully is crucial for survival in today's changing business world. Negotiation is fun if you know what you're doing.
Successful negotiators are assertive and challenge everything.
They know that everything is negotiable. It means thinking for yourself. You must be able to make up your own mind, as opposed to believing everything you are told. On a practical level, this means you have the right to question the asking price of that new car. You cannot negotiate unless you are willing to challenge the validity of the opposing position.