Yesterday, December 7th, was the memorial of St. Ambrose. His prayer as found in my missal is a most beautiful preparation for the Holy Sacrifice of the Mass, and I truly love to say it every morning.
Prayer of St. Ambrose
O loving Lord Jesus Christ, I a sinner, presuming not on my own merits, but trusting in Thy mercy and goodness, with fear and trembling approach the table of Thy most sacred banquet. For I have defiled both my heart and body with many sins, and have not kept a strict guard over my mind and my tongue. Wherefore, O gracious God, O awful Majesty, I, a wretched creature, entangled in difficulties, have recourse to Thee, the font of mercy; to Thee do I fly that I may be healed, and take refuge under Thy protection. And I ardently desire to have Him as my Savior, Whom I am unable to withstand as my Judge.
To Thee, O lord, I show my wounds, to Thee I lay bare my shame. I know that my sins are many and great, on account of which I am filled with fear. But I trust in Thy mercy, of which there is no end. Look down upon me, therefore, with the eyes of Thy mercy on me, who am full of misery and sin, Thou Who wilt never cease to let flow the fountain of mercy.
Hail, Victim of salvation, offered for me and for all mankind on the tree of the Cross. Hail, noble and precious Blood, flowing from the wounds of my crucified Lord Jesus Christ and washing away the sins of the whole world. Remember, O Lord, Thy creature, whom Thou hast redeemed with Thy Blood. I am grieved because I have sinned, I desire to make amends for what I have done.
Take away from me, therefore, O most merciful Father, all my iniquities and sins, that, being purified both in soul, and body, I may worthily partake of the Holy of Holies. And grant that this holy oblation of Thy Body and Blood, of which, though unworthy, I purpose to partake, may be to me the remission of my sins, the perfect cleansing of my offenses, the means of driving away all evil thoughts and of renewing all holy desires, the accomplishment of works pleasing to Thee, as well as the strongest defense for soul and body against the snares of my enemies. Amen.