Anger can be used to your benefit, says G. Richard Shell, a professor at the University of Pennsylvania's Wharton School of Business. "If your anger is a response to something unreasonable, unethical, or disrespectful," Shell says, "letting it show helps underline those perceptions so the other guy can take it seriously." But that doesn't mean kicking, screaming, or scratching. "Being angry and being aggressive are two different things," says Shell. It's OK to channel those impulses into a strong remark, such as "You’re making me really angry right now." Walking out of a negotiation is also not a bad thing, Shell says. The fact that you need to take a time-out tells the other party something important is at stake.