Nouwen was an extraordinarily gifted spiritual writer. Here’s a passage from his Out of Solitude, Conclusion that provides some very powerful reasoning for prayer by means of withdrawal to the lonely place.
(Mark 1:35) ” ‘In the morning, long before dawn, he got up and left the house, and went off to a lonely place and prayed there. When Simon and his companions found him, Jesus said: “Let us go—to the neighboring country towns, so that I can preach there too, because that is why I came.”
The words which Jesus spoke in these neighboring country towns were born in the intimacy with the Father. They were words of comfort and of condemnation, words of hope and of warning, words of unity and of division. He dared to speak these challenging words because he did not seek his own glory: “If I were to seek my own glory,” he says, “that would be no glory at all; my glory is conferred by the Father, by the one of whom you say, ‘He is our God,’ although you do not know him” (John 8:54). Within a few years Jesus’ words brought about his rejection and death. But the one who had spoken to him in the lonely place raised him up as a sign of hope and new life.
When you are able to create a lonely place in the middle of your actions and concerns, your successes and failures slowly can lose some of their power over you. For then your love for this world can merge with a compassionate understanding of its illusions. The your serious engagement can merge with an unmasking smile. Then your concern for others can be motivated more by their needs than your own. In short: then you can care. Let us therefore live our lives to the fullest but let us not forget to once in a while get up long before dawn to leave the house and go to a lonely place.”