Sadness...

anguish, blahs, bleakness...
blue devils, blue funk, broken heart, bummer...
cheerlessness...
dejection, depression, despondency, disconsolateness, dismals, dispiritedness, distress, dolefulness, dolor, down trip, downcastness, downer, dysphoria...
forlornness, funk...
gloominess, grief, grieving...
heartache, heartbreak, heavy heart, hopelessness...
letdown, listlessness...
melancholy, misery, moodiness, mopes, mournfulness, mourning...
poignancy...
sorrow, sorrowfulness...
the blues, the dumps, tribulation...
woe...