Throughout human history, the apostles of purity, those who have claimed to possess a total explanation, have wrought havoc among mere mixed-up human beings.
Happiness lies in being privileged to work hard for long hours in doing whatever you think is worth doing. One man may find happiness in supporting a wife and children. Another may find it in robbing banks. Still another may labor mightily for years in pursuing pure research with no discernible result. Note the individual and subjective nature of each case. No two are alike and there is no reason to expect them to be. Each man or woman must find for himself or herself that occupation in which hard work and long hours make him or her happy. Contrariwise, if you are looking for shorter hours and longer vacations and early retirement, you are in the wrong job. Perhaps you need to take up bank robbing. Or geeking in a sideshow. Or even politics.