What falls away is always?

不易流行
fu.eki.ryuu.kou

Literally: not – simple / divination / change – flow – go

Alternately: One of Bashō’s principles for writing haiku: that the essence of haiku lies in both the unchanging (不易) and in that which changes with the times or situation (流行). The principle of always incorporating something new, but without forgetting the parts that do not change.

In an alternate interpretation, this compound comments on the immutable nature of change itself; the idea that change alone is constant.