Niestzche is not my guru. He is just a dude with a cool philosophy about the world that I dig. In simplest terms, I utilize Nietzsche's philosophy not from a position of seeing his philosophy as prescriptive but more as descriptive. In other words, I do not read him as prescribing the right behavior patterns for everyone. But instead, I read him and see him better describing reality as it is compared to other philosophers and philosophies. For example, despite my own criticisms of certain aspects of his philosophy, I do find that Nietzsche's ideas best reflect reality as it is. For example, like Nietzsche, I also see two trajectories for humanity, one toward the "last man" or the higher men. I also see his concept of the will to power, as basically the force of life itself to procreate new forms, being manifest in the world. I see the will to power everywhere, from protoplasm to the origin and development of life through evolution, to capitalistic trade and economic grow, and even in the origination of our universe as a continually expanding force of plenty. All of this is better described by Nietzsche's Will to Power.
Whenever I find my own tendency toward idealism where I tend to demand that reality be different from what it actually is, I sense Nietzsche tapping me on my shoulder saying here is perhaps a better way to view reality. For example, even Christians today act not so Christ-like, they do not turn the other cheek, sale their possession to give to the less fortunate, and rarely leave the 99 for the one, etc. Instead of "Christ-likeness," I am more often instead slapped in the face with reality and the will to power: in that I instead experience men and women, even most Christians, displaying the mammalian instincts and Christians acting more like little "devils" rather than "saints." This is because in reality there is no Devil and our instincts are part of our evolved biology. So that what I actually experience is human mammals dressed up in "angel costumes" of pious performance, which is only an act. In reality, I experience human mammals with "dogs in their cellar" (as Nietzsche puts it), whether they are Christian or not. I see human mammalian instincts manifesting either in the form of law abiding healthy behavior (which builds trust and friendships) or in illegal and criminal ways. Nietzsche thus provides for me at least a more accurate mirror reflection of reality as it is, beyond supernatural notions of Good & Evil or Piety & Sin.
This video Why Nietzsche Loved Thucydides, does a good job showing why Nietzsche applauds Thucydides and Machiavelli as reality based thinkers who avoided Platonist Idealism and what REBT calls "Shoulding" on the world, and instead they mirrored reality as it is. As for myself, I find something odd in that when I take this more Nietzschean approach of seeing life, I am actually less frustrated and depressed by the reality I encounter in my daily life; and instead I have a more accepting attitude towards life because I'm not expected it to be something different than what it is. I'm not expecting people to be any different than who they are. I expect their fight or flight primate mammal instincts to kick in from time to time. I instead expect it and navigate accordingly.