In Zen teachings, impermanence is the first of the three marks of existence. Everything changes, nothing stays the same. The second mark of existence is no-self, which derives from the first: If everything changes and nothing stays the same, then there is no such thing as a fixed self. The self is only a passing notion, a changing story, relative to its momentary position in space and time. Suffering, the third mark of existence, derives quite logically from the first two. We don't like impermanence, we want to be someone, a fixed self, and we want that self to last. Lacking that fixity, we suffer.