Fable

Sandeep Guatam, at his blog The Mouse Trap has written a compelling series of posts under the general theme - If I'm happy, then A; If I'm sad, then B. These contrasting behaviors demonstrate regulatory significants of these two modes.

Guatam starts with Am happy, will seek novelty; am sad, will stick with the familiar. He summarizes this post and the whole series:

Promotion focus is expansive, is happy, is creative and long-term, and is novelty preferring versus prevention focus is restrictive, is sad, is focused on the task at hand, and is familiarity preferring. In other words people in safe environments having promotion focus are manic while those in unsafe environments and having prevention focus are depressive.

Next, Sad versus Fair:

I agree broadly with their thesis [Tan & Forgas (2010)] that sadness also has adaptive value and happiness should not be seen as all rosy and sadness all bad.

And from the cited study Tan & Forgas (2010):

Our findings confirm that negative affect often produces adaptive and more socially sensitive outcomes. For example, negative moods can improve the detection of deception, reduce judgmental errors, improve eyewitness accuracy, and improve interpersonal communication strategies. The present experiments confirm this pattern by demonstrating that mild negative moods also increase fairness and sensitivity to the needs of others.

Next, Deep Talk v. Small Talk:

Happy people spent more time talking to others in social settings versus spending time alone. Further, happy people spent much more time in substantive conversations than in making [small] talk. This was [reverse] in the case of sad people.

Next Paranoid/Gullible v. Realistic:

From Lount (2010):

The results in this article are consistent with work demonstrating that a positive mood increases reliance upon stereotypes and scripts in interdependent situations. More pointedly, the findings from all five experiments supported the predictions of the accommodation–assimilation model over mood-congruency models. This leads to a fairly strong conclusion that the relationship between positive mood and trust depends, in large part, on available schemas, cues, and stereotypes.

Gautam concludes:

Happiness leads to use of stereotypes/schema, leads to becoming more gullible/ paranoid... leading to psychoses. Although the present study did not had anything to say about sad mood (the contrast was with neutral mood) it is not unreasonable to extrapolate and claim that sad people are more realistic and depend on behavior of the other party rather than stereotypes...

The most recent entry, Despair/Ennui v. Anger/Irritability:

Happiness is opposed to ennui/despair while sadness is opposed to anger/irritability and while happiness is a measure of flourishing; sadness is a measure of illness.