Sources of emotions

Sleep quality affects mood. Undergraduates and adult workers who are sleep-derived report greater feelings of fatigue, anger and hostility.
One of the reasons why too little sleep, or poor sleep quality, puts people in a bad mood is that it impairs decision making and makes it difficult to control emotions.
A recent study suggests that a poor night's sleep also impairs people's job satisfaction the next day, mostly because they feel fatigued, irritable and less alert.