Strategies to change dynamics within a negotiation

The  power of anger: For the opponent to concede to your demands, rising anger is more effective than static anger and rising anger is more effective than either rising or static happiness.

A rising surge of anger elicits fear of possible escalation into conflict and fear of no deal at all, so the opponent wants to cut losses by giving in. But you are in trouble if you're negotiating on values, not goods or if there's a power imbalance.