Here then is another reason why apostles withdraw to make a retreat; they need to be charged with the Holy Spirit.The Holy Spirit is given to those who watch and pray and wait patiently, those who have the courage to get away from everything and get to grips with themselves and with God in solitude and silence. No wonder every one of the great prophets, and indeed Jesus himself, retired to the desert for long periods of silence, prayer, fasting, wrestling with the forces of evil. The desert is the furnace where the apostle and the prophet are forged. The desert and not the marketplace. The marketplace is where apostles function. The desert is where they are formed and seasoned and receive their commission and their message for their world, "their" gospel. (Emphasis mine)
-From Contact with God by Anthony De Mello