Prayer is how a Christian lives and breathes. (HT Cyberbretheren)
Chrystostom Book I, De Orando (On Prayer)
He who does not pray and have a heartfelt longing to speak with God in prayer certainly has no understanding or life in him. For it is a certain sign of great foolishness, to regard lightly or not understand such a great glory (to speak with God), also not to have a desire and love for prayer, and not be able to conceive of and understand that such is the sure indication of a human who is dead to God, who does not fall to his knees in prayer at the feet of the Lord Christ. For in the same way as this body is dead when there is no longer breath in it and the arteries cease to pulse, so is also the man dead in his soul and stinking, when in it there is no breath or pulse of anguish and of the heart. Therefore, if I see a person who does not love and value prayer, it is soon certain that there is no Christian understanding in him and that such a person is not adorned or endowed with the gifts of the Spirit.