Harvard psychologist Dan Gilbert, author of Stumbling on Happiness, challenges the idea that we’ll be miserable if we don’t get what we want. Our "psychological immune system" lets us feel truly happy even when things don’t go as planned.

Gilbert describes a study where patients suffering from amnesia were asked to rank several paintings in the order they like them. They were then told they could keep a painting from the middle of their rankings. After the researchers left the room the patients quickly forgot about the whole encounter. When asked to rank the paintings again, however, they ranked the one they owned as being the best.

This means that our tastes are often sculpted by what we have available. As Gilbert points out, our psychological immune system can keep us happy even through depressing circumstances.