...he spent whole days and nights over his books; and thus with little sleeping and much reading his brains dried up to such a degree that he lost th… - Miguel de Cervantes

Finally, from so little sleeping and so much reading, his brain dried up and he went completely out of his mind.

with little sleep and much reading his brains got so dry that he lost his wits.

And thus, from too little sleep and too much reading, his brain dried up and he completely lost his judgment.

"By God and upon my conscience", said the devil, "I never observed it, for my mind is occupied with so many different things that I was forgetting the main thing I came about." "This demon must be an honest fellow and a good Christian," said Sancho; "for if he wasn't he wouldn't swear by God and his conscience; I feel sure now there must be good souls even in hell itself."

All I know is that while I’m asleep, I’m never afraid, and I have no hopes, no struggles, no glories — and bless the man who invented sleep, a cloak over all human thought, food that drives away hunger, water that banishes thirst, fire that heats up cold, chill that moderates passion, and, finally, universal currency with which all things can be bought, weight and balance that brings the shepherd and the king, the fool and the wise, to the same level. There’s only one bad thing about sleep, as far as I’ve ever heard, and that is that it resembles death, since there’s very little difference between a sleeping man and a corpse.

Well, the same thing happens in the drama and business of this world, where some play emperors, others pontiffs, in short, all the figures that can be presented in a play, but at the end, which is when life is over, death removes all the clothing that differentiated them, and are all equal in the grave.