"The inner life is lived in a strange enough world; for in truth each man and woman dwells in a different environment—so different that I believe that there are not two people who have so much as half of it in common. Men know each other's inner world so slightly that they neglect this difference, and it is only when two people have a relation of utter love and trust that their inner lives begin to become perceptible to each other and are revealed as mutually most strange."
January 1, 1970
https://en.wikiquote.org/wiki/Introspection