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.
God, unto whom all hearts are open, unto whom all will
is spoken, unto whom nothing is hidden,
I beseech Thee to cleanse the intent of my heart
with the unspeakable gift of Thy grace that
I may perfectly love Thee and worthily praise Thee.