Well idk if happiness is really first place, everyone decides for himself but I can't imagine how our ancestors could win second world war or send people into space if they placed happiness as number one priority.
But ofcourse "remember they guy that gave up? Neither does anybody else".
I agree that we might not all have "happiness" as our first objective, but whatever your #1 goal is, achieving it gives you a certain satisfaction, and thus the feeling of happiness. The conception of happiness is different from a person to another, and it is hidden in each of our objectives.