Thomas Merton has written: "It is in the deserts of loneliness and emptiness that the fear of death and the need for self-affirmation are seen to be illusory. When this is faced, then anguish is not necessarily overcome, but it can be accepted and understood. Thus, in the heart of anguish, are found the gifts of peace and understanding: not simply in personal illumination and liberation, but by commitment and empathy, for the contemplative must assume the universal anguish and the inescapable condition of mortal man. The solitary, far from enclosing himself in on himself, becomes every man. He dwells in the solitude, the poverty, the indigence of every man." (Raids on the UnSpeakable)
How can we understand what Merton is saying?
First, there is something common to the nature of persons. The deeper you go inside people, the more we are the same. I have called the loci of human similarity as "ontological dualities." For example, every person struggles with Trust vs. Control; Faith vs. Fear; Rejection vs. Affirmation; Death vs. Life; and so on.
Secondly, when a solitary contemplative allows God to search out the deep waters of their own heart (Proverbs 20:5), they come in contact with what is common to all persons, and therefore what is most important in all persons in the sense of getting at the heart of personhood. This is the area of the "heart" that Jesus talked about in contradistinction to the superficial self which is exterior and "white-washed."
Thirdly, God made persons in his image. The imago dei is in us all.
Therefore, in the depths of each solitary human heart lies that which is most like God, is in all persons, and needs "renovation" (see Dallas Willard's Renovation of the Heart).
This is the meaning of Merton's words - "The solitary, far from enclosing himself in himself, becomes every man. He dwells in the solitude, the poverty, the indigence of every man."
The solitary contemplative, then, is on a great mission. It is to, by the help of the Holy Spirit, bring freedom to the real self, and consequentially become a spiritual guide for others to find the same freedom.