14. Many who practice the commandments think they are following the spiritual path. But they have not yet reached the city, and in fact remain outside it. For they travel foolishly, deviating unawares from the straight highway into side-roads, not realizing how close the vices are to the path of virtue. For the true fulfillment of the commandments demands that we do neither too little nor too much but simply pursue a course acceptable to God and in accordance with His will. Otherwise we labor in vain and do not make straight the paths of the Lord (cf. Isa. 40:3). For in everything we do we must be clear about the goal we are pursuing.
15. To be on the spiritual path means seeking the Lord in your heart through fulfilling the commandments. For when you listen to John the Baptist crying in the wilderness, ‘Prepare the way of the Lord, make His paths straight’ (Matt. 3:3), you must understand that he is referring to the commandments and their fulfillment both in the heart and in actions. It is impossible to ‘make straight’ the path of the commandments and to act rightly unless your heart too is straight and upright.
~ St Gregory of Sinai, Philokalia V4.215