For Nietzsche ideals were a remnant of religion and curse upon humanity because they devalued reality itself, a negation of life.
The last thing I should promise would be to "improve" mankind. No new idols are erected by me; let the old ones learn what feet of clay mean. Overthrowing idols (my word for "ideals")—that comes closer to being part of my craft. One has deprived reality of its value, its meaning, its truthfulness, to precisely the extent to which one has mendaciously invented an ideal world. ( Ecce Homo)
The scientific revolution cast doubt on the Stoic and Christian belief in a divine and purposeful cosmos but left intact the idea that the cosmos was ordered and discernible to human reason. This said Nietzshe was nothing more than human projection, a comforting faith in the face of a meaningless and chaotic universe - "a sea of forces flowing and rushing in perpetual flex" (Will to Power). If even scientific laws are idols, what then is left?
Nietzsche central theory was that is not possible to separate judgement or ideals from the person holding them. Rather these judgement or ideals should be understood as symptoms or expressions of an individual psychology. To prove this theory Nietzsche turned away from logic and epistemology and instead opted for genealogy.
Genealogy reveals the hidden origin of values and ideals by placing them within earthly history dragging them away from the the sacred and the transcendental - "There are no facts, only interpretations". He condemned grand scientific and religious systems as laying claim to entities not available to the senses and were hence devaluing the physical world to create an intelligible world of logic and maths. Science and religion strip away our senses and our bodies - religion in favor of the transcendental and science because it is suspicious of the subjective. This stripping away of our senses and bodies is what Nietzsche called reactive: "Whatever needs first to have itself proven to be believed is of little value".
So while science and religion were reactive, art was active because an artist does not repress the human senses to create a false world. Rather artists impose meaning and judgments without debate or discussion or first proving propositions. Language in science and in philosophy is an instrument to discover a higher reality or truth. Language in art and poetry is an end in itself, creating an effect of those experiencing it.
But Nietzsche was no liberator who sought to remove the alienation caused by science and logic so we could become 'fully human'. Rather he sought to reconcile the active and the reactive, a reconciliation that would create the only true ideal that unlike his idols would be removed from life:
Man makes the best discoveries about culture within himself when he finds two heterogeneous powers governing there. Given that a man loved the plastic arts or music as much as he was moved by the spirit of science, and that he deemed it impossible to resolve this contradiction by destroying the one and completely unleashing the other power, the only thing remaining to him is to turn himself into such a large hall of culture that both powers can be accommodated within it, even if at opposite ends, while between there reside mediating powers with the strength and authority to settle, if need be, any quarrels that break out. Such a hall of culture within the single individual would, however, bear the strongest resemblance to the cultural structure of entire epochs and, by analogy, provide continual instruction about them. For wherever grand cultural architecture has developed, its purpose has been to effect a harmony and concord between contending powers through an overwhelming assemblage of the other powers, but without the need to suppress them or clasp them in irons. (Human, all too Human)
Nietzsche wished to reconcile the active and the reactive without contradiction resulting in harmful divided emotions like guilt. It was this reconciliation that Nietzsche termed the 'grand style' and is the center of his ethics. The good life for Nietzsche is the passionate life lived with harm any - "To master the chaos within himself, to compel his chaos to become form", to become logical simple, unambiguous, mathematical , to make oneself the law.. The infamous and misunderstood will to power is the will to live a intense life free of internal conflicts. It is the "will to will" to live free of guilt, remorse and regret.
We have seen how Nietzsche sought to replace grand theories of ontology and epistemology with genealogy designed to reveal the earthly origin of ideals; We have seen Nietzsche ethics was the grand style of life lived passionately without regret or remove. But how is this to be accomplished? In two ways: eternal recurrence and amor fati.
If God is dead and the idols we erected to replace him are smashed, what is left to us? What is left must be earthly and part of life, not another idol or reality to condemn life itself. Nietzsche answer, only partly articulated before his death, is surprisingly mundane :
My doctrine says: to live in such a way that you must wish to live again - you will in any case! If striving gives you the highest feeling, then strive! If rest gives you the highest feeling, then rest! ... Only make sure you come to know the highest feeling, and spare no means . Eternity is at stake! This doctrine is mild in its treatment of those who do not believe in it. It has neither hell or threats. But anyone who does not believe merely lives a fugitive life in the consciousness of it.
If the cosmos has no meaning or purpose, then all is chaos stretching into eternity without beginning or end. Energy or "world forces" then must never deplete but repeat and renew constantly. This he called eternal recurrence:
Whatever state this world can attain, it must have attained it and not once but countless times. Take this moment: it has already been once and many times and will return… Man: Your whole life will be turned over like an hourglass time and again…
If there is nothing but eternal recurrence, then all we have is amor fati or "love of what the present brings" :
My formula for greatness in a human being is amor fati: that one wants nothing to be different, not forward, not backward, not in all eternity. Not merely bear what is necessary, still less conceal it—all idealism is mendaciousness in the face of what is necessary—but love it. (Ecce Homo)
But Nietzsche seems to fall afoul of the same trap he accused Stoicism of: wanting to love the present as it is but also wanting to select the moments we are willing to live in infinite recession. However his doctrine of eternal recurrence was never fully fleshed out before his death.
I think Nietzsches philosophy has a certain glamour. His writings are filled with poetic and highly quotable pose that can make comprehension difficult and often echo soundlessly off the walls. Having attacked the values and ideals which we live for, he can ultimately offer little more than Stoicism stripped of its cosmology and theology. His importance lies in the birth of the postmodern movement with it's suspicion of cultural values and ideals. But they leave us with nothing but economics - the ultimate amor fati for the wealthy.