“In order to pray in this way, we must bear in mind the method of prayer, how it is possible to pray without ceasing, i.e. to pray with the mind. We can always do this, it only we desire it. While we are occupied with handiwork, while we walk, while we eat or drink–we can always pray with the mind, or perform mental prayer pleasing to God, true prayer. With our body let us work, but with our soul let us pray.”

(St. Gregory Palamas , 14th Century Theologian, ex. on mental prayer)