HOW CAN WE BE HAPPY?

In a book called The Progress Paradox, Gregg Easterbrook points out that despite our average quality of life having risen on a number of different indices, we are less happy than we once were. (By "we", I mean a very crudely sampled average person on an average salary in a developed country.)

Why is this? And why were people in Ghana, where I lived for a couple of years, generally happy and optimistic even though they had so little?

Is it the lack of God, time, generosity of spirit? A poor diet? Too many unfulfilled expectations? What is it that we lack? What do you think?