In a bad mood? Don't worry - according to research, it's good for you.
An Australian psychology expert who has been studying emotions has found being grumpy makes us think more clearly.
In contrast to those annoying happy types, miserable people are better at decision-making and less gullible, his experiments showed.
While cheerfulness fosters creativity, gloominess breeds attentiveness and careful thinking, Professor Joe Forgas told Australian Science Magazine.
'Eeyore days'
The University of New South Wales researcher says a grumpy person can cope with more demanding situations than a happy one because of the way the brain "promotes information processing strategies".
He asked volunteers to watch different films and dwell on positive or negative events in their life, designed to put them in either a good or bad mood.
Next he asked them to take part in a series of tasks, including judging the truth of urban myths and providing eyewitness accounts of events.
Those in a bad mood outperformed those who were jolly - they made fewer mistakes and were better communicators.
Professor Forgas said: "Whereas positive mood seems to promote creativity, flexibility, co-operation and reliance on mental shortcuts, negative moods trigger more attentive, careful thinking, paying greater attention to the external world."
The study also found that sad people were better at stating their case through written arguments, which Forgas said showed that a "mildly negative mood may actually promote a more concrete, accommodative and ultimately more successful communication style".
His earlier work shows the weather has a similar impact on us - wet, dreary days sharpened memory, while bright sunny spells make people forgetful.
