Morality is as old as humanity, and there have been many different kinds of morality across the millennia. Moral philosophers today lack this historical perspective, and in searching for a "rational foundation" for morality, all they really do is try to justify their own morality. Unable to see outside the perspective of their own morality, they are unable to see the concept of morality itself as problematic and needing to be questioned and justified.
Anything great that we have achieved or become has been the result of a strict obedience in one particular direction over a long period of time. Great art, thinking, and spirituality has occurred through constant and harsh discipline. Only through a kind of enslavement and hardship can we refine ourselves.
Nietzsche asserts that we actually register far less than we think we do. For instance, when we see a tree, we don't see the detail of every branch and leaf, but only glance at the rough shape of the whole, and from that construct all the smaller details in our head. Similarly when we read a book, we really take in only a few words and then fit those words into what we already think we know. In this sense, Nietzsche suggests, we are all inventors, artists, and liars: our so-called "knowledge" is our own make-believe.
People differ not only in what they think is worth pursuing, but also in what they take to be possession of what they pursue. One man may feel he "possesses" a woman if he can have sex with her, while another feels this possession is only worthwhile if the woman is willing to give up everything for him. This second kind of possession is made the more valuable the more deeply the woman knows the man, so the man must be able to make himself known to her as best he can. Nietzsche also uses examples of charity and education as means of possession. For instance, in educating, the teacher makes the child see the world according to the teacher's perspective; the teacher thus comes to possess another soul.
Nietzsche bemoans the "slave revolt in morality," which considered the rich, violent, and sensual to be evil, while considering the poor holy. We have come to see everything healthy, dangerous, and passionate about ourselves as pathological. This morality of the "herd" claims in the name of "happiness" that we should avoid our darker instincts. This may be true for some, but Nietzsche despises moralizers precisely because they generalize on matters that depend greatly on the individual. There have always been more people obeying than commanding, but simply because the majority is suited to submissiveness we should not conclude that this is a general principle that all should obey. Nowadays, those who command are almost ashamed of it, and dare only do so if they do it in the name of God, the law, or the people.
Nietzsche suggests that our moral valuations are based largely on fear. In a community that is safe from external threats, any aggressive members of that community come to be seen as a threat. Thus, our morality condemns all that is lively, preferring the safety of a tamed, mediocre mass. This morality of the "herd" then proclaims itself as the only true morality (other moralities are "immoral") and as the savior of the herd.