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.
Silence provides an atmosphere for prayer, and it preserves the growth that has been gained in prayer. People who begin to speak immediately after prayer in common, will not be able to preserve the fruits of their prayer. Their Recollection is dissipated, and they pour out all that has been accumulated within them. The observance of silence, on the other hand, allows the spirit of prayer to reverberate and take root in the heart.