From "Ascent of Mount Carmel" by John of the Cross.
In order to arrive at having pleasure in everything,
desire to have pleasure in nothing.
In order to arrive at possessing everything,
desire to possess nothing.
In order to arrive at being everything,
desire to be nothing.
In order to arrive at knowing everything,
desire to know nothing.
In order to arrive at that wherein you have no pleasure,
you must go by a way wherein you have no pleasure.
In order to arrive at that which you know not,
you must go by a way that you know not.
In order to arrive at that which you possess not,
you must go by a way that you possess not.
In order to arrive at that which you are not,
you must go through that which you are not.
When thy mind dwells upon anything, you are ceasing to cast yourself upon the All. For, in order to pass from the all to the All, you have to deny yourself wholly in all. And, when you come to possess it wholly, you must possess it without desiring anything. For, if you will have anything in having all, you have not your treasure purely in God.
In this detachment the spiritual soul finds its quiet and repose; for, since it covets nothing, nothing wearies it when it is lifted up, and nothing oppresses it when it is cast down, because it is in the centre of its humility; but when it covets anything, at that very moment it becomes wearied.