We must never forget that we are bound to perfection and should aim ceaselessly for it. The practice of mental prayer is necessary to reach that goal. Because it is the breath of life for our soul, holiness is impossible without it. It is only in mental prayer and spiritual reading that we cultivate the gift of prayer. Mental prayer is greatly fostered by simplicity-- that is forgetfulness of self and of the body and of the sense, and by frequent aspirations that feed our prayer.

(Blessed Mother Teresa of Calcutta, No Greater Love)