There is no great genius without some touch of madness
"The mind cannot express anything lofty and above the ordinary unless inspired. When it despises the common and the customary, and with sacred inspiration rises higher, then at length it sings something grander than that which can come from mortal lips. It cannot attain anything sublime and lofty so long as it is sane: it must depart from the customary, swing itself aloft, take the bit in its teeth, carry away its rider and bear him to a height whither he would have feared to ascend alone."
By Seneca, On Tranquility of the Mind