Like someone whose eyes, when lifted up after staring at a book for a long time, wince at the mere sight of a naturally bright sun, so too, when I lift my eyes from looking at myself, it hurts and stings me to see the vivid clarity and independence-from-me of the world outside, of the existence of others, of the position and correlation of movements in space. I stumble on the real feelings of others. The antagonism of their psyches towards mine shoves me and trips up my steps. I slide and tumble above and between the sounds of their strange words in my ears, the hard and definite falling of their feet on the actual floor, their motions that really exist, their various and complex ways of being persons who are not mere variants of my own.
— Pessoa, The Book of Disquiet (trans. R. Zenith)
Notes from a Room 
X tells me he doesn’t like to imagine other people’s lives, the minds of others. He can’t even think about it for too long. The very idea’s like a threat, he mutters. He can only relate to people who think exactly like him, he says, and of course no one does, there’s always a remainder, something that doesn’t quite fit, that threatens his peace of mind. The idea that other minds exist unsettles him, he says, horrifies him. He’s learned not to trust the similarities between himself and others, he says. So he puts a buffer between himself and others, he says. What else can he do? he asks. Even an empty fortress is better than the alternative, he says, the awful strangeness of another mind.
https://notesfromaroom.com/2009/05/09/the-minds-of-others