How we cite our quotes: (Chapter.Section.Paragraph) or (Chapter.Paragraph)
Quote #7
Man not only effects a change of form in the materials of nature; he also realizes his own purpose in those materials. And this is a purpose he is conscious of, it determines the mode of his activity with the rigidity of a law, and he must subordinate his will to it. This subordination is no mere momentary act. Apart from the exertion of the working organs, a purposeful will is required for the entire duration of the work. This means close attention. The less he is attracted by the nature of the work and the way in which it has to be accomplished, and the less, therefore, he enjoys it as the free play of his own physical and mental powers, the closer his attention is forced to be. (7.1.2)
The idea here is that it's natural for work on a project to eventually take control of the worker. Workers must subordinate their will long-term to the requirements of their projects. The more they care about a project, the more they'll be okay with the commitment required to work on something. But under capitalism, many workers become so specialized that they don't develop a relationship with the entire commodity they're producing. Their job might have them simply standing on a production line turning the same screw over and over, since that's what might be most efficient and therefore most profitable.
Quote #8
The labour process, as we have just presented it in its simple and abstract elements, is purposeful activity aimed at the production of use-values. It is an appropriation of what exists in nature for the requirements of man. It is the universal condition for the metabolic interaction between man and nature, the everlasting nature-imposed condition of human existence, and it is therefore independent of every form of that existence, or rather it is common to all forms of society in which human beings live. (7.1.21)
Marx is somewhat romantic about the labor process. He sees work as the purposeful use of nature in order to sustain life. He opposes capitalism, but sees nothing inherently degrading about the labor process—only in what the labor process becomes under the capitalist mode of production.
Quote #9
On the other hand, the working day does have a maximum limit. It cannot be prolonged beyond a certain point. This maximum limit is conditioned by two things. First by the physical limits to labour-power. Within the 24 hours of the natural day a man can only expend a certain quantity of his vital force. Similarly, a horse can work regularly for only 8 hours a day. During part of the day the vital force must rest, sleep; during another part the man has to satisfy other physical needs, to feed, wash and clothe himself. Besides these purely physical limitations, the extension of the working day encounters moral obstacles. The worker needs time in which to satisfy his intellectual and social requirements, and the extent and the number of these requirements is conditioned by the general level of civilization. The length of the working day therefore fluctuates within boundaries both physical and social. (10.1.4)
Capitalists and workers fight over the length of the working day, but nature has something to say about it as well. By nature, people have to rest a certain number of hours in order to function at all. So the working day has to include time for rest if capitalists want their workers to stay alive.