Why do you think the pursuit of personal happiness is unachievable? The assumption is that every person allows with no impediment every other person to find his or her own happiness and NOT be prevented from doing so. And please don't insult me by going on about some nutters pursuit of being happy killing people or stealing or doing something that impedes someone else's idea of happiness. To fulfill the promise all people must stop telling everyone else how to live. And that includes governments. For instance there have been groups of people in the UK concerned about wasting energy and climate change. They have been gluing themselves to roads, bridges etc causing huge traffic jams and inconvenience. Whose right to pursuit of happiness would prevail in the USA?