And we ought to bear the absence of friends cheerfully, just because everyone is bound to be often absent from his friends even when they are present. Include among such cases, in the first place, the nights spent apart, then the different engagements which each of two friends has, then the private studies of each and their excursions into the country, and you will see that foreign travel does not rob us of much. 11. A friend should be retained in the spirit; such a friend can never be absent. He can see every day whomsoever he desires to see.

—Seneca, Letters from a Stoic