Mark Roberts, on his excellent blog, has recently finished a series of posts dealing with happiness. Here's the link to Mark's thoughts on the subject.
Last summer, I tackled the same topic in a series. Here are the links to each installment of what I called, The Happiness Project:
The Poverty That Leaves You Rich
The People Who Make a Difference
The Diet That Will Make You Happy
What Mercy Does
The People Who See God
The People Who Make Peace
Happy When the World Turns Away
I hope that you find both Mark's and my articles helpful.