Focus on interests, not positions, but do build large agreements on small prior doables. Be caretaker of the other's welfare as well as your own. Make agreements that meet objective, reasonable standards of fairness. Make agreements that meet the needs of both, and that build the relationship. Express anger constructively.
Emotions are legitimate and communicate.
Channel anger's energy. Focus on the angering behavior, not the person. Define your best alternative to a negotiated agreement. Seek a third party facilitator when you and the other lack needed skills or when there seem to be intractable differences. Hear the other's anger non-defensively.