"Pray as you can, and don't try to pray as you can't"

Having quoted John Chapman on abandon, I thought I might also quote from the portion of the book that transfixed me when I was in college.  Also, by the way, here is a thoughtful article on Chapman (PDF) by Sarah Coakley.

All those who find it impossible to meditate [in the Western sense of considering Biblical events or doctrines with the intellect], not from laziness or lukewarmness, and find they cannot fix their thoughts on a subject, or understand the meaning of the words unless they cease to feel that they are praying, are meant to cease all thinking, and only make acts of the will....
Let the acts come. Do not force them. They ought not to be fervent, excited, anxious, but calm, simple, unmeaning, unfelt...We are not to know what we mean. To some God may some day give more definite knowledge and love; but I speak to beginners. Let us be thankful if we are like this for no more than twenty years...
The time of prayer is passed in the act of wanting God. It is an idiotic state, and feels like the completest waste of time, until it gradually becomes more vivid. [Those, by the way, are the two sentences that changed my life.] The strangest phenomenon is when we begin to wonder whether we mean anything at all, and if we are addressing anyone, or merely repeating mechanically a formula we do not mean. The word God seems to mean nothing. If we feel this curious and paradoxical condition, we are starting on the right road, and we must beware of trying to think what God is and what He has done for us, etc, or what we are before him, because this takes us out of prayer and spoils God's work, as St. John of the Cross says...
Distractions are of two kinds: a) the ordinary distractions, such as one has in meditation, which take one right away, and b) the harmless wanderings of the imagination alone, while the intellect is (to all appearances) idle and empty, and the will is fixed on God. These are quite harmless.
When these latter distractions remain all the time, the prayer is just as good, often much better. The will remains united; yet we feel utterly dissatisfied and humbled. But we come away wanting nothing but God.
The real value of prayer can be securely estimated by its effect on the rest of the day.

I've found many other Christian practitioners of prayer since who wrote more beautifully, or thoroughly, or inspiringly about contemplation. But Chapman got in on my ground floor. The book was nearly impossible to find for years, but has been reprinted recently.