Happiness does not come from a state, but from a change of state. That it is so is illustrated by the total failure of every writer to describe a satisfactory paradise, whether in heaven or on earth. The tedium of eternity has almost become a joke, and the description of the earthly utopias are no better. Most of them fail to recognize that the human mind cannot hold any emotion for long at an even intensity, but that it always degenerates into something much more tepid… But it is not simply a change of state that makes for happiness; there must be something unexpected about it.
— Charles G. Darwin (1887-1962)