Daniel Kahneman won a Nobel prize for Prospect Theory (at least I think that's what he won it for).

From my notes:

"Individuals evaluate uncertain outcomes with reference to context rather than absolute scales.

Consequences:
1a - people put a much higher value on something they already own than they would pay for the same thing if was offered for sale
1b - fairness affects economic decision
1c - people cannot imagine what effect adaptation to their circumstances will have on happiness.

2 - people care twice as much about avoiding losses as they do about making gains.
3 - people cannot predict how their own tastes will change
4 - people generally make decisions based on memories rather than original experience"

I could write a book on applying just this one principle in life.