Essentially, prayer is attentiveness to God, and this has various degrees, from weak or faltering to total. This attentive attitude is itself the fruit of love; God's love becomes the dominant commitment of the will. The person has achieved purity of heart and spiritual wholeness. Joy takes hold of the heart, transmuting every moment into the irresistible attraction and power of divine love.
If the heart wanders or is distracted, bring it back to the point quite gently -- and even if you do nothing during the whole of your prayer but bring your heart back, though it went away every time you brought it back, your time would be very well employed.