I have to agree that people over-use the term, but we still have a long way to go in order to accept what it really is.

I have and have had close relatives with severe depression. My aunt had severe depression for almost a year. When she went to the doctor, he told her "Just go home, woman! You don't have anything." She jumped off a bridge in front of a train 5 years ago, two days after her 41st birthday. My other aunt was depressed for two years and she got over it with - you will not believe - sports and painting.

I think I am a happy person, though I have my sad moments as anybody else. I just try to not sink in my self-pitty and bad mood, but also not denying the reason for being upset. Analyzing yourself, your reasons for acting one way or another, looking for what could improve your mood or your life, and taking your responsibilities to other people to the fullest helps a lot.