Excerpt from Cloud of Unknowing
We must therefore pray in the height, depth, length, and breadth of our spirits. Not in many words, but in a little word of one syllable. What shall this word be? Su such a word as is suited to the nature of prayer itself. And what word is that? First let us see what prayer is in itself, and then we shall know more clearly what word will best suit its nature.
In itself prayer is nothing else than a devout setting of our will in the direction of God in order to get good, and remove evil. Since all evil is summed up in sin, considered causally or essentially, when we pray with intention for the removing of evil, we should neither say, think, nor mean any more than this little word 'sin'. And if we pray with intention for the acquiring of goodness, let us pray, in word or thought or desire, no other word than 'God'. For in God is all good, for he is its beginning and its being. Do not be surprised then that I set these words before all others. If I could find any shorter words which would sum up fully the thought of good or evil as these words do, or if I had been led by God to take some other words, then I would have used those and left these. And that is my advice for you too.
But don't study these words, for you will never achieve your object so, or come to contemplation; it is never attained by study, but only by grace. Take no other words for your prayer, despite all I have said, than those that God leads you to use. Yet if God does lead you to these, my advice is not to let them go, that is, if you are using words at all in your prayer: not otherwise. They are very short words. But though shortness of prayer is greatly to be recommended here, it does not mean that the frequency of prayer is to be lessened. For as I have said, it is prayed in the length of one's spirit, so that it never stops until such time as it has fully attained what it longs for. We can turn to our terrified man or woman for an example. They never stop crying their little words 'Help' or 'Fire!' till such time as they have got all the help they need in their trouble.