One of the Fathers said, "The Christian who only remembers to speak with God when it is the given time for prayer, has not yet learnt how to pray."

Prayer, according to its quality, is communion and union of man with God, by its action it upholds the world. It is reconciliation with God. It is the mother, but also the daughter, of tears. It is the atonement  of sins, a bridge over temptations, a wall against affliction, a crushing of conflicts, a work of Angels, the food of the Incoporeal, future gladness, boundless work, source of virtues, cause of grace, invisible progress, food of the soul, illumination of the mind, an axe against despair. a proof of hope, a cure for sorrow,  the wealth of monks, the treasure of hesychasts, the reduction of anger, the mirror of progress, the demonstration of stature, an indication of one's condition, a relevation of future things, a sign of glory. For one who truly prayers, prayer is the court, the judgment  hall and the tribunal of the Lord before the judgement to come.

St. John of the Ladder

If God is slow in answering your request, and you ask but do not promptly receive anything, do not be upset, for you are not wiser than God. When you remain as you were before, without anything happening, it is either because your behaviour is not worthy of your request, or because the paths in which your heart was travelling were far removed from the aim of your prayer, or because  your interior condition is far too childish, when compared with the magnitude of the thing for which you have asked.

St. Isaac of Nineveh [Syria], The Syriac Fathers on Prayer and the Spiritual Life.

An Elder once said that the Soul  needs  the four following things: to fear God's Judgement, to hate sin, to love virtue and to pray without ceasing.

Once, an abbot of a certain monastery,  founded by St. Epiphanios, Bishop of Cyprus, visited the Saint and said with some satisfaction,"With your blessing Master, we have not neglected the prayer-rule you gave us. We read the first, the third, the sixth and the ninth hour most willingly."
    "And what do you do during the other hours?" the Holy Hierarch said in surprise. "Do you not occupy yourself with prayer? If you do not, then you are not monks.
    Seeing the abbot's puzzlement the Holy Bishop explained. " whoever belongs to the order of monks is duty bound to occupy himself in psalmody and prayer. Even though the Prophet David was both a king and a warrior, he prayed in the evening, at midnight he got up from his bed to glorify God together with the angels. We still find him in prayer before dawn. As soon as day breaks, he raises up his heart to give thanks to his Creator. He prayed yet again in the morning , and at midday and he knelt down to call on God. He himself tells us that he praised the Lord seven times a day."

A father said: The Christian who only remembers to converse with God only whenn it is the set time for prayer has not yet learnt to prayer.