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.
Although the mind's natural state is one of peace, for most of us this peace lies hidden beneath the distorting veils of faulty perceptions, thoughts and beliefs. Peace has become something that must be rediscovered and remembered through training the mind to correct its distortions. Only by training the mind to correct distorted thoughts and perceptions can the gift of peace be experienced. Peace of mind is clearly an internal matter. It must begin with your own thoughts and then extend outward. It is from your peace of mind that a peaceful perception of the world arises.