Decades ago, Richard Nixon popularized the "madman theory" of negotiations. It suggested that demonstrating a willingness to consider "madness" in action would provide you with negotiating leverage. If your adversary believed that you really might do something extreme or even self-destructive, then you held more of the negotiating power, even if you were too rational ever to actually carry out the threat.

Consider trying this madman approach when you negotiate your next business deal: start by being nice and cheerful, then flash some anger. Repeat as often as necessary, but always in that order. Never start with anger. It will throw your opponents off balance, making them think you're unpredictable, if not a bit unbalanced, and they may be more willing to make concessions because of the uncertainty that a deal will get done.