Sources of emotions and moods

Have you ever said, "I got up on the wrong side of the bed today"?
Have you ever snapped at a co-worker or family member for no particular reason? If you have, it probably makes you wonder where emotions and moods come from. Here, we discuss some of the primary influences:

personality, time of day, day of the week, weather, stress, social activities, sleep, exercise, age, gender.