This thread got me thinking so I googled the American concept of happiness, apparently the concept of happiness has changed over time. Happiness was once thought to be good luck and favorable external circumstances but is now considered to be an internal feeling. No wonder it is so elusive for most of us.
Also "the pursuit of happiness" makes more sense when applied to the first definition. To pursue favorable external surroundings and good luck(fortune) makes more sense to me than pursuing some ambiguous internal state of being.