Happiness. Simple concept, hard to achieve. I believe that most people are not happy. They are not necessarily unhappy (miserable), but they are not truly happy either. [Now I am talking about your every day Joe, as there is no point in discussing why an orphan in Afghanistan is unhappy.] So why do I think people are so unhappy (sorry, I was not able to secure a grant to perform a study on 17 people over a span of 17 years, so I am just going to have to go with my guts):-
(1) People do not know what is it that they really want in life. This sounds like I am stating the obvious -- if you don't know what is it that you want, you never be able to attain it. And so long as you don't attain it, or working towards attaining it, there will always be that void in your life. [Perhaps people who are deeply devoted don't have that void. I would not know; I do not have a religion. Perhaps they filled that void by convincing themselves that that is the ultimate goal, and to perform charity acts in the name of their religion. Or perhaps they deal with that void by telling themselves to look forward to the after life.]
(2) Expectations in life. Different cultures/different family backgrounds put expectations on individuals, let it be be successful, get married, have kids, be skinny, etc. etc. Sometimes, sometimes, one just need to come to the realization that it is their own lives, and if it's too painful to pursue or live up to those expectations, at some point you will just have to let it go. And if your family/culture cannot grasp that idea, they, and you, will just have to deal. [I think is is the reason why Asian American females have the highest suicidal rate among all groups in US. The expectation became ridiculous, and they are stuck not knowing how to get out of bond.]
(3) Expectations causing one to not question whether this is what one really wants. For example, most cultures/families expect their kids to get married and have kids. Whilst that is the norm in the society, they are not meant for everyone. If you disagree with me, explain to me why marriage is being portrayed in such negative light some times?
When one is constantly being brainwashed as to what is expected of them/what is the norm, only the more enlightened ones will be able to stop in the path and really think about, "wait, is this truly what I want?"
(4) Settling -- this one is more an individual's own fault rather than those around them. People settle, even on important things like jobs/partners. How many of your coworkers express that they love their jobs? Not that many, I bet. Sure, in an economic downturn, we all have to take what we can get. I am by no means recommending that one should stick to their principles while starving and living on the street. But how many have you known who'd gripe till their heads fall off about how much they hate their jobs, but won't do anything about it? I don't know about you, but I have personally seen one too many relationships in which at least one of those involved were contemplating about breaking up, only turned around and ended up getting married. Ugh.
(5) Generally stupidity -- not as in low IQ, that actually has nothing to do with happiness. Many stupid people are happy like a clam. We should be envious of them. I am referring to those who make stupid decisions in life -- getting married for the wrong reasons, i.e. being pregnant; having kids for the wrong reasons, i.e. in an effort to save a failing relationship. Okay, buddy, you have nobody to blame but yourself.