You seem to be going through a temporary slump

Everyone gets depressed on occasion; in fact, it's a healthy, normal feeling, especially after a crappy day. However, if feeling overwhelmed, overworked, helpless or under-appreciated becomes the norm for more than two weeks, or worse -- life starts to feel not worth living, you could be entering into a deeper mood disorder. "What we might expect to occur as a normal reaction to say a breakup...may be [considered] 'short term,'" said Dr. Sponholz. "But other factors may make it 'longer term,' such as if the person also is dealing with job loss, financial stress, recent death of a loved one, and abusing alcohol."

Pay attention to any concern expressed by people whose opinions you respect, and whether depression could be manifesting itself in a less noticeable way, such as a tendency to be a workaholic, over-exercise, over-eat or -drink, or even overdo it with plastic surgery or shopping sprees. Take time to relax and focus on your health and passions in life, whether it's through exercise, a hobby such as writing or cooking, or a vacation. And remind yourself not to stress about things that are beyond your control.

If none of these things seem to be lifting your mood, consider seeing a therapist (it doesn't mean you're "crazy" -- a major misconception, says Dr. Sponholz). Find a licensed mental health services specialist in your area.