Zenit.org has a nice commentary on this Sunday's Gospel reading by Fr. Raniero Cantalamessa, who is the Preacher to the Papal Household (meaning he's the guy who gets/has to preach to the Pope). Fr. Cantalamessa writes about Jesus' instructions to his disciples in the Gospel of Luke to pray always without growing weary. Here's an excerpt from the commentary:
"This ideal of constant prayer is realized in different forms in the East and West. Eastern Christianity practiced it with the 'Jesus Prayer': 'Lord Jesus Christ, have mercy on me!'
"The West formulated the principle of constant prayer in a more flexible way so that it could also be proposed to those who do not lead a monastic life. St. Augustine teaches that the essence of prayer is desire. If the desire for God is constant, so also is prayer, but if there is no interior desire, then you can howl as much as you want -- to God you are mute.
"Now, this secret desire for God, a work of memory, of need for the infinite, of nostalgia for God, can remain alive, even when one has other things to do: 'Praying for a long time is not the same thing as kneeling or folding your hands for a long time. In consists rather in awakening a constant and devout impulse of the heart toward him whom we invoke.'
"Jesus himself gave us the example of unceasing prayer. Of him, it is said that he prayed during the day, in the evening, early in the morning, and sometimes he passed the whole night in prayer. Prayer was the connecting thread of his whole life.
"But Christ’s example tells us something else important. We are deceiving ourselves if we think that we can pray always, make prayer a kind of respiration of the soul in the midst of daily activity, if we do not set aside fixed times for prayer, when we are free from every other preoccupation."
For me, the practice of praying always is something I've only ever been able to get a very feeble and tenuous (and brief) grasp of. I've found it difficult to maintain for very long, mostly because my will is just so weak and I am so easily distracted by silly things. But those days when I am able to live in constant awareness of God's presence and when I am continually seeking His face are just so indescribably joyous. It's a sad commentary on myself that I could experience such periods joy in the presence of God, but then let them slip away because of the effort of the will involved. I must pray for God's grace that I might persevere in loving and desiring Him in every moment of my life.