Feeling low is a natural part of life and it is completely normal to feel a bit disheartened or upset from time to time, especially after a major life change or a distressing event. However, for some people, understanding their mood can be a real issue and this is something that can occur frequently and for no apparent reason. If this happens for an extended period of time, then it may be a sign of depression or hormonal imbalances. Those who suffer from low mood often report that they feel tired, frustrated, worried and lacking in confidence.