I've never forgotten Richard Sibbes' The Bruised Reed. It's one of a few lasting memories from my Puritan study days: words that stick in your mind and sing to your heart long after you've laid down the book.
Here it is, quoted by Challies:
A Christian complains he cannot pray.
"Oh, I am troubled with so many distracting thoughts, and never more than now!"
But has he put into your heart a desire to pray? Then he will hear the desires of his own Spirit in you.
"We do not know what to pray for as we ought" (nor how to do anything else as we ought), but the Spirit helps our infirmities with "groanings too deep for words" (Rom. 8:26)..."My sighing is not hidden from you" (Psa. 38:9).
God can pick sense out of a confused prayer...
Sometimes a Christian has such confused thoughts that he can say nothing but, as a child, cries, "O Father", not able to express what he needs...These stirrings of spirit touch the heart of God and melt him into compassion towards us...
"Oh, but is it possible", thinks the misgiving heart, "that so holy a God should accept such a prayer?" Yes, he will accept that which is his own, and pardon that which is ours...
Look at the promises: "Call upon me in the day of trouble: I will deliver you" (Psa. 50:15). "Ask, and it shall be given to you" (Matt. 7:7).
God accepts our prayers, though weak, because we are his own children, and they come from his own Spirit; because they are according to his own will; and because they are offered in Christ’s mediation, and he takes them, and mingles them with his own incense (Rev. 8:3).
There is never a holy sigh, never a tear we shed, which is lost.
And as every grace increases by exercise of itself, so does the grace of prayer. By prayer we learn to pray. So, likewise, we should take heed of a spirit of discouragement in all other holy duties, since we have so gracious a Saviour.
Pray as we are able, hear as we are able, strive as we are able, do as we are able, according to the measure of grace received. God in Christ will cast a gracious eye upon that which is his own...
Let us not be cruel to ourselves when Christ is thus gracious.
There is a certain meekness of spirit whereby we yield thanks to God for any ability at all, and rest quiet with the measure of grace received, seeing it is God’s good pleasure it should be so...
When, with faithful endeavor, we come short of what we would be, and short of what others are, then know for our comfort, Christ will not quench the smoking flax.
You can read the rest here.