Generating physical warmth and showing signs of disappointment are examples of negotiation techniques. The former is more appropriate before a negotiation, while the latter is a technique that is effective during the negotiation.
To cause the other party to behave in a friendlier manner and be more susceptible to reaching an agreement with you, offer them warm beverages and keep the room temperature warm. Holding something warm, such as a cup of coffee, is likely to influence the other party's mood positively.
Showing signs of disappointment during a negotiation may cause the other party to agree to greater compromises on their part. Subtly expressed disappointment signals to the other party that they have offered less than what was expected and moves them to provide compensation.