Mood is the emotion which is sustained over some time. Normally mood changes with various circumstances, triggers, even our own thoughts, so it's the quality of the mood to be changeable and that is its essence because a human being has to have appropriate emotions according to situations. For example If someone hears some bad news, feeling bad is natural, likewise listening to favorite music lifts mood and that's also natural. If your mood swings aren't excessive, then it's normal but if you think it's otherwise please consult.
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