In isolated, rare cases this portion of madness may well have been the
means which held such an excessively scattered nature firmly together: in
the lives of individuals, too, delusions often have the value of curatives,
which are actually poisons. Yet in the case of every "genius"
who believes in his divinity, the poison at last becomes apparent, to the
degree that the "genius" grows old. One may recall Napoleon, for
example: surely through that very belief in himself and his star,
and through a scorn for men that flowed from him, his nature coalesced into
the mighty unity that distinguishes him from all modern men, until finally
this same belief turned into an almost mad fatalism, robbed him of his quick,
penetrating eye, and became the cause of his downfall.
The Gay Science