Prayer is profitable and speedful to be used for the getting of purity of heart by destroying of sin and bringing in virtues; not that thou shouldst thereby make our Lord know what thou desirest, for He knoweth well enough what thou needest, but to dispose thee and make thee ready and able thereby, as a clean vessel, to receive the grace which our Lord would freely give thee, which grace cannot be felt till thou be exercised and purified by the fire of desire in devout prayer. For though it be so that prayer is not the cause for which our Lord giveth grace, nevertheless it is a way or means by which grace freely given cometh into a soul. (John Climacus)

Humility begins by listening. In listening for God is the foundation of humility and of prayer.

In such prayer we can know with simultaneous strength the depth of sin that separates us from God and the staggering height of God's love for us.

Be still and know I am (Psalm 46).