As we get older the portions of our life that do not enter into our ordinary relations become greater and greater. Most of our friends know nothing of large passages in our lives, so that an increasing part of our past experience is excluded from most of our personal relations. The inevitable result is that as men grow older they come to feel more solitary, and when they meet a friend of long ago, this feeling is suddenly relieved.
出典：Bertrand Russell: On old friends,Jan. 4th, 193３. In: Mortals and Others, v.1 (1975)