The pain of a loss is almost twice as strong as the reward felt from a gain.
According to Wikipedia:
Loss aversion is the tendency to prefer avoiding losses to acquiring equivalent gains. The principle is prominent in the domain of economics. What distinguishes loss aversion from risk aversion is that the utility of a monetary payoff depends on what was previously experienced or was expected to happen.
Loss aversion was first indentified by Amos Tversky and Daniel Kahneman.
Also, losses are twice as powerful, psychologically, as gains.