"One who has made the discovery of his inner solitude, or is just about to make it, may need considerable spiritual help. A wise man, who knows the plight of the new solitary, may with the right word at the right time spare him the pain of seeking vainly some long and complex statement of his case. No such statement is necessary: he has simply discovered what it means to be a man. And he has begun to realize that what he sees in himself is not a spiritual luxury but a difficult, humiliating responsibility: the obligation to be spiritually mature."
Photo by Thomas Merton
-- Thomas Merton, Notes for a Philosophy of Solitude, in the book Disputed Questions (New York: Farrar, Straus and Cudahy, 1960) p. 189
Update: There's an interesting article in today's New York Times, "Kierkegaard, Danish Doctor of Dread", that speaks to the need for solitude, and its relationship to the anxiety of being alone. Look how similar this paragraph is to Merton's:
"In his “Works of Love,” Kierkegaard remarks that all talk about the spirit has to be metaphorical. Sometimes anxiety is cast as a teacher, and at others, a form of surgery. The prescription in “The Concept of Anxiety” and other texts is that if we can, as the Buddhists say, “stay with the feeling” of anxiety, it will spirit away our finite concerns and educate us as to who we really are, “Then the assaults of anxiety, even though they be terrifying, will not be such that he flees from them.” According to Kierkegaard’s analysis, anxiety like nothing else brings home the lesson that I cannot look to others, to the crowd, when I want to measure my progress in becoming a full human being."