Nietzsche saw Being as a myth at times, but neither the Buddha nor Nagarjuna ever saw Being as a “myth.” Rather, they saw it as a delusion that humans superimpose upon the world. It was Nietzsche, especially the Nietzsche of Twilight of the Idols, who saw Being as a myth.
What Nietzsche and Buddhism do have in common is the tendency to psychologize even static fields of knowledge – to submit even fixed natural laws to introspection, mind, and moods. A major tenet of Buddhist philosophy can be succinctly summed up as a “pre-reflective commitment to substance metaphysics.”
Nietzsche did not believe in a unified subject, but nor did he commit to a complete empirical disentangling of the subject the way the Buddha did. To Buddha, the individual could famously be reduced to elementary-pieces (skadhas). To use an analogy from Zen writer Brad Warner, the skadhas are like a junk heap – remove the pieces of junk, and there’s no heap. Nietzsche would never accept such a degrading perspective for his Overman – he would view it as fraught with nihilism. (And though this is often misunderstood, Nietzsche was indeed an anti-nihilist.)
To Nietzsche, pain and pleasure are a false polarity because in Nietzsche’s thinking, pain is simply the resistance that one must break through when one wishes to exercise acts of power in the world. Similarly, compassion is worthless to Nietzsche, unless it is the compassion of those who are strong. To Nietzsche, weak people who suffer will infect their compassion with their own suffering and thus only make things worse.