Depression.

[HotRoddin]

First understand that its not unusual to be down ... everyone gets down ... sometimes its for a reason ... sometimes its at random ... sometimes its deep and profound ... sometimes you hardly notice it ... sometimes it lasts a long time ... sometimes it passes quickly .... its part of life, we all share it. You gotta move on, keep occupied, break the routine but most of all don't dwell on it ... think about the things that make you happy and don't dwell on the things that don't.

"The're ain't no good or bad life Wyatt, theres just life"
(Doc Holiday to Wyatt Earp in Tombstone)