Sleep, Wonderful Sleep.....

One of the biggest problems for most people's mental health is that they don't get enough sleep and the sleep they do get is not deep enough to give them restful sleep.
When we don't have enough sleep we have more anxiety, get more depressed and feel overwhelmed by things we can usually manage when we are well rested.
One of the first questions I ask people when they come to see me is if they are sleeping well.  I'd say upwards of 80% report sleep problems of one kind or another.  They either have trouble falling asleep or wake up repeatedly during the night and often can't fall back to sleep.
I found this interesting article that addresses some of the ways people sabotage their own sleep:
www.care2.com/greenliving/top-10-sleep-mistakes-and-their-solutions.html

Once you have a pattern of disrupted sleep it creates itself as a pattern and needs to be broken.  Just like having depression over an extended period of time may change your body chemistry, so does lack of sleep.
Try getting yourself to sleep regularly for an extended period of time and see if that doesn't help improve your mood.