Be constant in your practice, and one day the One who gave you the desire for the prayer of the heart will give you that prayer itself. When your heart's intention is fixed on God, it will keep lit the incense of your prayer, and wind of distraction will not put it out. do not worry about stray thoughts; they may come and go, but they will not take your attention away from God.
The fitness of our hearts and thoughts to receive God's spirit is like that of violin strings. If they are properly tuned, in harmony with one another, then the touch of the bow produces beautiful music. If not, then there is only discord. Whenever our hearts are truly ready to receive God's spirit, they will produce heavenly airs and joyous harmonies -- both in this life and in the spiritual world.