This prayer, traditionally ascribed to St. Basil of Caesarea (c. AD 329-379), is one of the great prayers/meditations for use after having received the Holy Mysteries of Christ. It deftly makes its way through the meaning of the Eucharist both as a participation in Christ's life now and in the future, orienting us towards the Kingdom of God of which the Eucharist is both first-fruits and promise of a fuller harvest. Together with the Post-Communion prayer in the liturgy, it is an effective expression of gratitude for sharing in Body and Blood of Christ and a guide to the Church's belief about the meaning of this Sacrament.
The prayer also recalls that what we receive in the liturgy is to be lived out in holy lives every day...something essential to a holistic, non-hypocritical faith. The Holy Communion both challenges us and gives us the grace to live that challenge. Note, too, that the prayer is both an "I" and a "We" prayer--effectively expressing both the corporate and individual nature of Christian life.
This prayer may be said immediately after the Dismissal at the Eucharist's conclusion, or at a time later in the day following worship.
O Master Christ God, King of the ages and Creator of all things, I thank You for all the good things which You have bestowed upon me, and for the communion of Your most pure and life creating Mysteries. I pray You, therefore, O Good One and Lover of mankind: Keep me under Your protection and in the shadow of Your wings; and grant me, even until my last breath, to partake worthily, with a pure conscience, of Your Holy Things, for the remission of sins and life eternal. For Your are the Bread of life, the Source of holiness, the Giver of good things; and unto You do we send up glory, together with the Father and the Holy Spirit, now and ever, and unto the ages of ages. Amen.