Letters 63.10

If we have other friends, we surely deserve ill at their hands and think ill of them, if they are of so little account that they fail to console us for the loss of one. If, on the other hand, we have no other friends, we have injured ourselves more than Fortune has injured us; since Fortune has robbed us of one friend, but we have robbed ourselves of every friend whom we have failed to make.

Seneca, Letters to Lucilius 63.10, translated by Richard Mott Gummere