There are many prayers in Augustine's Confessions (c. AD 400). All through his written journey he talks to God. In Book I he begins with, "...you made us for yourself and our hearts find no peace until they rest in you." And, “On your exceedingly great mercy rests all my hope. Grant what you command, and command what you will.” (Confessions, X:29)
Here is a prayer from Book X:69-70 that I've adapted for congregational use, perhaps before Communion:
“How you have loved us, O good Father, who did not spare your only Son, but delivered him up for us who are wicked! How you have loved us, for whom your Son became obedient unto death, even death upon the cross! He had power to lay down his life and power to take it up again, and for us he became to you both Victor and Victim. For us, he became both Priest and Sacrifice. Out of slavery he made us your sons. Our hope is fixed upon him, who will heal all our diseases, who sits at your right hand and intercedes for us. Otherwise we would utterly despair, for our infirmities are many and great! But your medicine is greater still!
"You have strengthened us by saying, 'since Christ died for all, those who live should no longer live for themselves, but for him who for their sake died and was raised.' Behold, O Lord, we cast all our cares upon you, that we may live and 'behold wondrous things out of your law.' You know our infirmities! Teach us and heal us. Your only Son--he 'in whom are hidden all the treasures of wisdom and knowledge' has redeemed us by his blood.
"We will keep him before us, and will eat and drink and will share our food and drink. For we are poor and desire to be satisfied from Christ, together with those who eat and are satisfied in him, as it is written, 'The poor will eat and be satisfied; they who seek the LORD will praise him...'" (Psalm 22:26 NIV)