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.
There is a Wisdom that arises--sometimes gracefully, sometimes gently, sometimes awkwardly, sometimes fiercely, but it will arise to save us if we let it, and it rises from WITHIN us, like the force that drives green shoots to break the winter ground, it will arise and drive us into a great blossoming like a pear tree, into flowering, into fragrance, fruit and song ... in that part of ourselves that can never be defiled, defeated or destroyed, but that comes back to life, time and time again, that lives--always--that does not die.