People tend to wake up in a good mood and they are happiest on weekends.
That trend is confirmed by a study of Twitter activity. Researchers looked at English-language tweets from 2.4 million in 84 countries. They used a computer program that searched for words indicating positive mood -- happy, enthusiastic, brilliant -- or negative mood -- sad, anxious, fear.
They found that unless you're a night owl, a positive attitude peaks early in the morning and again near midnight. It starts to dip in mid-morning before rising again in the evening.
But it's not just work-related stress that causes that dip. A researcher points out that the same midday dip occurs on the weekend. He says the pattern is probably due to the effects of sleep and our 24-hour biological clock.