When we look deeply at the nature of things, we see that in fact everything is impermanent. Nothing exists as a permanent entity; everything changes. It is said that we cannot step into the same river twice. If we look for a single, permanent entity in a river, we will not find it. The same is true of our physical body. There is no such thing as a self, no absolute, permanent entity to be found in the element we call "body." In our ignorance we believe that there is a permanent entity in us, and our pain and suffering manifest on the basis of that ignorance. If we touch deeply the nonself nature in us, we can get out of that suffering.
— Thich Nhat Hanh