Negotiating Mistakes

In Fast Company: Good points, but not not quite enough about how to achieve them.  A particular sales mistake I remember well:   

" ... Talking too much is a sure-fire way to kill a deal. In fact, Lewis-Fernandez says it’s not unusual for a salesperson to talk so much about a product or service that they talk you right out of the purchase. ... “Never underestimate the power of silence,” she says. “There’s an old adage: ‘He or she who speaks next loses.’ When discussing a deal, if you simply stop talking and get comfortable with the awkwardness of silence, your ability to win your argument, sell the product, or a get concession in the negotiation increases significantly.” ... "