What do you know of happiness? It's written into the Declaration of Independence as something the individual is free to pursue ... but what is it, really?
In the nuts and bolts definition department, happiness is subjective; it is a determination that a person's current situation and concept of the good life are getting along nicely. True happiness comes from positive relationships, not stuff and not special places to go. In fact, to be truly happy, you need to make other people happy (Bible verses abound). Happiness is a byproduct of a life well lived with others, reaching out that helping hand, lifting up the folks around you, and being willing to accept others attempts to make you happy (accept the compliment graciously, don't be too proud to humbly accept help offered out of the goodness of another's heart)! Above all, true happiness can never come at the expense of others. Real happiness has a very moral component.
Happiness as so defined will elude those who seek it in consumerism (sorry advertisers), in fleeting and ephemeral pleasure/thrill seeking, and ruthless competition for limited resources against others in a pitched battle for dominance. No long-term happiness there. See how countercultural happiness has become?
Viewing happiness through this lens, unhappiness can become a very useful gauge of what is going on in the world around you. If a person is persistently, chronically unhappy, it's time for the individual to look around and assess his or her relationships with others. Has too much time been spent at the office? Have social relations with friends and family deteriorated? Has too much emphasis been placed on the next shiny thing or the accumulation of wealth for its own sake? Be objective here with your subjective state ... you'll learn something useful.
On a larger scale, if unhappiness exists and persists in a group you are a part of or a group near you, it is likely that group is suffering from some sort of injustice or abuse ... and could use a helping hand.
Returning to that nuts and bolts definition, it seems to me that if your concept of the good life is skewed to either the bright and shiny thing end or to the I must martyr myself for others end, happiness will always elude you. Happiness as defined and explored here requires resetting that concept of the good life to include positive relationships with others. This leads me to a fascinating link with the Old and New Testaments. In both, righteousness is defined as being in right relations with God and each other. It's about loving others as self, being willing to serve others (and humble enough to be served), and having faith enough to trust others. So, I guess, the righteous person in the Bible is a happy person, not a hectoring, forbidding person.
For more, see the Dictionary of Pastoral Care and Counseling, p. 494.