The Word or absolution, I say, is what you should concentrate on, magnifying and cherishing it as a great and wonderful treasure to be accepted with all praise and gratitude.

If all this were clearly laid out, and along with that if the needs that ought to move and induce us to confession were clearly indicated, there would be no need of coercion or force. Their own consciences would persuade Christians and make them so anxious that they would rejoice and act like poor, miserable beggars who hear that a rich gift of money or clothes is being given out at a certain place; they would hardly need a bailiff to drive and beat them but would run there as fast as they could so as not to miss the gift.

Suppose, now, that the invitation were changed into a command that all beggars should run to the place, with no reason being given and no mention made of what they were to seek or receive there. How else would beggars go but with resentment, not expecting to receive anything but just letting everyone see how poor and miserable they are? Not much joy or comfort would come from this, but only a greater hostility to the command.

-- Martin Luther, "A Brief Exhortation to Confession" from The Large Catechism in Robert Kolb, ed., The Book of Concord, 476.

The painful effort which prayer involves is no proof that we are doing something we were not created to do.

If we were perfected, prayer would not be a duty, it would be a delight. Some day, please God, it will be. The same is true of many other behaviors which now appear as duties. If I loved my neighbor as myself, most of the actions which are now my moral duty would flow out of me as spontaneously as a song from a lark or a fragrance from a flower. Why is this not so yet? Well, we know, don't we? Aristotle has taught us that delight is the "bloom" of an unimpeded activity. But the very activities for which we were created are, while we live on earth, variously impeded: by evil in ourselves or in others. Not to practice them is to abandon our humanity. To practice them spontaneously and delightfully is not yet possible. This situation creates the category of duty, the whole specifically moral realm.

It exists to be transcended. Here is the paradox of Christianity As practical imperatives for here and now the two great commandments have to be translated "Behave as if you loved God and man." For no man can love because he is told to. Yet obedience on this practical level is not really obedience at all. And if a man really loved God and man, once again this would hardly be obedience; for if he did, he would be unable to help it. Thus the command really says to us, "Ye must be born again."

-- C.S. Lewis, Letters to Malcolm: Chiefly on Prayer

St. Ignatius of Loyola (I think it was) advised his pupils to begin their meditations with what he called a compositio loci. [...] If I started with a compositio loci I should never reach the meditation. The picture would go on elaborating itself indefinitely and becoming every moment of less spiritual relevance.

There is indeed one mental image which does not lure me away into trivial elaborations. I mean the Crucifixion itself; not seen in terms of all the pictures and crucifixes, but as we must suppose it to have been in its raw, historical reality. But even this is of less spiritual value than one might expect. Compunction, compassion, gratitude - all the fruitful emotions - are strangled. Sheer physical horror leaves no room for these. Nightmare. Even so, the image ought to be periodically faced. But no one could live with it. It did not become a frequent motive of Christian art until the generations which had seen real crucifixions were all dead.
--C. S. Lewis, Letters to Malcolm: Chiefly on Prayer