Some background on Contrition from Chatechism:
CCC 1431 – Interior repentance is a radical reorientation of our whole life, a return, a conversion to God with all our heart, and end of sin, a turning away from evil, with repugnance toward evil actions we have committed. At the same time it entails the desire and resolution to change one’s life, with hope in God’s mercy and trust in the help of his grace. This conversion of heart is accompanied by a salutary pain and sadness which the Fathers called animi cruciatus (affliction of spirit) and compunction cordis (repentance of heart).
CCC 1451 – [In the sacrament of reocnciliation] Among the penitents acts contrition occupies first place. Contrition is “sorrow of the soul and detestation for the sin committed together with the resolution not to sin again”.
CCC 1452 – When it arises from a love by which God is loved above all else, contrition is called “perfect” (contrition of charity). Such contrition remits venial sins; it also obtains forgiveness of mortal sins if it includes the firm resolution to have recourse to sacramental confession as soon as possible.
CCC 1453 – The contrition called “imperfect” (or “attrition”) is also a gift of God, a prompting of the Holy Spirit. It is born of consideration for sin’s ugliness or the fear of eternal damnation and the other penalties threatening the sinner (contrition of fear). Such a stirring of conscience can initiate an interior process which, under the prompting of grace, will be brought to completion by sacramental absolution. By itself, however, imperfect contrition can not obtain the forgiveness of grave sins, but it disposes one to obtain forgiveness in the sacrament of penance.
I grew up using the following prayer supplied by the church, and continue to use this during the sacrament of reconciliation:
(1) Oh my God, I am sorry for my sins with all my heart. In choosing to do wrong and failing to do good, (2) I have sinned against you whom I should love above all things. (3) I firmly intend with your help, (4) to do penance, (5) to sin no more, (6) and to flee from whatever leads me to sin. (7) your son Jesus Christ suffered and died for us, in his name Lord have mercy.
I use this while in the confessional with the priest. This helps me make sure I am bowing to his authority as I beg his forgiveness. It is not my own language, however, and in confession I am seeking a mending of the personal relationship with his will. To add the personal element I find saying a personal translation of the traditional act of contrition a useful self-imposed act of penance and a helpful practice to dispose myself to refusing to take his forgiveness for granted. The personal translation of this prayer, is as follows:
(1) My God, you are good. You have blessed me with life itself. You have poured your fullness of life into me. I have perverted it and turned it against you. You have laid before me the means and knowledge of your will, and I have chosen against you and found emptiness. (2) I have squandered your inheritance on emptiness which is not good, and have denied your blessings the chance to flourish into the life for the world you intended them to be. (3) Draw and hold me close to you Lord. (4) Only you can bring life from death. Live in me that I may replace the life I squandered. (5) Live in me that I may squander your life no more. (7) Your son Jesus Christ suffered and died that we may eat of his body and drink of his blood and enter into his life. (6) Let me also be sacrificed, that my attachment to that which is empty may be burned so that I too may be resurrected into new life.