Loss Aversion - the tendency for people to strongly prefer avoiding losses rather than acquiring gains. A by-product of this is Endowment Effect where people value the things they own more than identical products that they don’t own. In other words, people often demand much more to give up an object than they would be willing to pay to acquire it.
Decision theory in economics, psychology, philosophy, mathematics, and statistics is concerned with identifying the values, uncertainties and other issues relevant in a given decision, its rationality, and the resulting optimal decision. It is closely related to the field of game theory as to interactions of agents with at least partially conflicting interests whose decisions affect each other.