Everyone has moods.
Moods are a normal part of everyday life.
Daily life events, sleep, weather, physiological cycles, etc. Mood disorders are distinct from normal moods in their depth and persistence, and in their interference in one's ability to function. I knew that things weren't going that well lately, but I felt like I was punched in the gut when she told me she had met someone else whom she was interested in. Since then I've felt really awful. I'm with friends, but when I'm alone, or when something reminds me of her, I feel really down.