Nichiren Daishonin states in “Letter to Lord Niike”:
Deep in the Snow Mountains lives a bird called Kankucho which, tortured by the numbing cold, cries that it will build a nest in the morning. Yet, when the day breaks, it sleeps away the hours in the warm light of the morning sun without building its nest. So it continues to cry vainly throughout its life. The same is true of people.