This is St. Thomas Aquinas - After Holy Communion prayer.
I thank You, O holy Lord, almighty Father, eternal God, who have deigned, not through any merits of mine, but out of the condescension of Your goodness, to satisfy me, a sinner, Your unworthy servant, with the precious Body and Blood of Your Son, our Lord Jesus Christ.
I pray that this Holy Communion be not a condemnation to punishment for me, but a saving plea for forgiveness.
May it be to me the armor of faith and the shield of goodwill.
May it be the emptying out of my vices and the extinction of all lustful desires; an increase of charity and patience, humility and obedience, and all virtues, a strong defense against the snares of all my enemies, visible and invisible; the perfect quieting of all my evil impulses of flesh and spirit, binding me firmly to You, the one true God, and a happy ending of my life.
I pray too that You will deign to bring me, a sinner, to that ineffable banquet where You, with your Son and the Holy Spirit, are to Your saints true light, fulfillment of desires, eternal joy, unalloyed gladness, and perfect bliss. Through Christ our Lord. AMEN.