The Jesus Prayer is a prayer of marvelous versatility. It is a prayer for beginners, but equally a prayer that leads to the deepest mysteries of the contemplative life. It can be used by anyone, at any time, in any place: standing in queues, walking, traveling on buses or trains; when at work; when unable to sleep at night; at times of special anxiety when it is impossible to concentrate upon other kinds of prayer. But while of course every Christian can use the Prayer at odd moments in this way, it is a different matter to recite it more or less continually and to use the physical exercises which have become associated with it. Orthodox spiritual writers insist that those who use the Jesus Prayer systematically should, if possible, place themselves under the guidance of an experienced director and do nothing on their own initiative.