This quotation runs counter to Jefferson's "pursuit of happiness," and yet we understand that Jefferson was talking about the right of an individual to pursue his or her own dream, whatever it is in life that makes one happy.
What we have to come to terms with, however, is that a life of happiness is not the result of pursuing happiness for its own sake. It is the result of the life we live, the contribution we make, the service we offer, the experiences we are able to enjoy, the relationships we build and benefit from, the challenges we overcome and the sense of accomplishment that we have as we look back over the years.
True happiness is a byproduct. It is the result of how we live.