It is often quite helpful to read good examples of prayer. Recently, Pastor Steve Thomas recommended to me Lancelot Andrewes' Devotions. Andrewes was a bishop in the Church of England and a translator of the King James Bible. Here is a confession of sin which he wrote for morning prayer.
THOU Lover of men:
Thou that art very pitiful, the Father of mercies that art rich in mercy to all that call upon Thee,
I have sinned against Heaven and in Thy sight and am no more worthy to be called Thy son, nor to be made one of Thy hired servants, no, not the lowest.
But I repent.
Woe is me.
Help Thou mine impenitence, and if there be any comfort of love by Thy bowels and mercies, by the multitude by the riches of Thy grace, by Thy abundant mercy, by the great love wherewith Thou hast loved us, be merciful to me a sinner.
Be merciful to me, of all sinners the greatest, the most wretched.
Deep calleth unto deep, the deep of our misery unto the deep of Thy Compassion; where sin hath abounded there let grace much more abound; overcome our evil of Thy good; let Mercy rejoice against Judgment.
But beyond and before all things, I believe that Thou art the Christ, the Son of the living God;
Thou that didst come into the world to save sinners of whom I am chief,
Thou that didst come to redeem the lost, let not one whom Thou hast redeemed perish.
Deliver me from the recollection of evil things, that what I have seen and heard from the wicked I may never remember, nor ever tell to others; that I may hate every evil way.
I have deserved death, but yet I appeal from the Tribunal of Thy Justice to the Throne of Thy Grace.