The crown of every good endeavor and the highest of achievements is diligence in prayer. Through it, God guiding us and lending a helping hand, we come to acquire the other virtues. It is in prayer that the saints experience communion in the hidden energy of God’s holiness and inner union with it, and their intellect itself is brought through unutterable love into the presence of the Lord.
…Just as the work of prayer is greater than other work, so it demands greater effort and attention from the person ardently devoted to it, lest without him being aware the devil deprives him of it….he must keep strict watch, so that fruits of love and humility, simplicity and goodness–and, along with them, fruits of discrimination–may grow daily from the constancy of his prayer. These will make evident his progress and increase in holiness, thus encouraging others to make similar efforts.
~St Makarios of Egypt (paraphrased by St Symeon Metaphrastis)