So, feeling irritable can be a useful thing for humans. I firmly believe that current trends toward mood control through medication is a circumvention of what is ultimately good for us...
BBC NEWS | Health | Feeling grumpy 'is 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