The Imitation of Christ, by Thomas a Kempis, tr. by William Benham , at sacred-texts.com
Above all things the priest of God must draw nigh, with all humility of heart and supplicating reverence, with full faith and pious desire for the honour of God, to celebrate, minister, and receive this Sacrament. Diligently examine thy conscience and with all thy might with true contrition and humble confession cleanse and purify it, so that thou mayest feel no burden, nor know anything which bringeth thee remorse and impedeth thy free approach. Have displeasure against all thy sins in general, and specially sorrow and mourn because of thy daily transgressions. And if thou have time, confess unto God in the secret of thine heart, all miseries of thine own passion.
2. Lament grievously and be sorry, because thou art still so carnal and worldly, so unmortified from thy passions, so full of the motion of concupiscence, so unguarded in thine outward senses, so often entangled in many vain fancies, so much inclined to outward things, so negligent of internal; so ready to laughter and dissoluteness, so unready to weeping and contrition; so prone to ease and indulgence of the flesh, so dull to zeal and fervour; so curious to hear novelties and behold beauties, so loth to embrace things humble and despised; so desirous to have many things, so grudging in giving, so close in keeping; so inconsiderate in speaking, so reluctant to keep silence; so disorderly in manners, so inconsiderate in actions; so eager after food, so deaf towards the Word of God; so eager after rest, so slow to labour; so watchful after tales, so sleepy towards holy watchings; so eager for the end of them, so wandering in attention to them; so negligent in observing the hours of prayer, so lukewarm in celebrating, so unfruitful in communicating; so quickly distracted, so seldom quite collected with thyself; so quickly moved to anger, so ready for displeasure at others; so prone to judging, so severe at reproving; so joyful in prosperity, so weak in adversity; so often making many good resolutions and bringing them to so little effect.
3. When thou hast confessed and bewailed these and thy other shortcomings, with sorrow and sore displeasure at thine own infirmity, make then a firm resolution of continual amendment of life and of progress in all that is good. Then moreover with full resignation and entire will offer thyself to the honour of My name on the altar of thine heart as a perpetual whole burnt-offering, even by faithfully presenting thy body and soul unto Me, to the end that thou mayest so be accounted worthy to draw near to offer this sacrifice of praise and thanksgiving to God, and to receive the Sacrament of My Body and Blood to thy soul's health. For there is no oblation worthier, no satisfaction greater for the destroying of sin, than that a man offer himself to God purely and entirely with the oblation of the Body and Blood of Christ in the Holy Communion. If a man shall have done what in him lieth, and shall repent him truly, then how often soever he shall draw nigh unto Me for pardon and grace, As I live, saith the Lord, I have no pleasure in the death of a sinner, but rather that he should be converted, and live. All his transgressions that he hath committed, they shall not be mentioned unto him.(1)
(1) Ezekiel xviii. 22, 23.