Prayer, according to Jesus, is life. Prayer isn't a doctrine or a duty; it is bread, or better, breath. Jesus lived prayer. He not only joined in the formal prayers in synagogue and temple, but also he prayed in the middle of a meeting, walking along a road, facing intense suffering, and experiencing conflict. The Name of God was constantly on his lips. His words were heart-deep, as if drawn up from a well of an inner life that was, regardless of outer circumstances, in constant communion with God.
And he taught his disciples to "pray always and not lose heart" (Luke 18.1). "Keep alert," so God doesn't "find you asleep when he comes suddenly." So, "keep awake" through the practice of unbroken communion with God (Mark 13.33-36).
Christ's disciples followed his example. Saint Paul lived a life of prayer, and urged it upon all believers. "Pray without ceasing," (1 Thessalonians 5.17). "Pray in the Spirit at all times. Keep alert and always persevere in supplication for all the saints" (Ephesians 6.18).
Prayer, then, is life and life is prayer.