Saint Pio Hearing Confessions
When I first became Catholic, I would alternate between saying the official Act of Contrition (see below) and one that I would make up by myself.
For those that are not Catholic, when a Catholic goes to confession, it goes like this:
Bless me Father for I have sinned, it has been (2 weeks) since my last confession and I accuse myself of the following sins:
Here we list sins by kind and number
For these sins and those I cannot now remember and for my sins against charity toward God and neighbor, I humbly repent and ask for counsel, penance, and absolution.
Here, the priest gives advice or exhortation and imposes a penance (e.g. "say 3 Our Fathers and 3 Hail Marys").
And then the priest says, Now if you'll make an Act of Contrition I will give you absolution. This proves that we really are sorry and not just going through the motions.
We say the Act of Contrition and then the priest absolves us by saying: "I absolve you of your sins in the name of the Father and of the Son and of the Holy Spirit."
Now the "Act of Contrition" is a prayer that we say to God and the priest listens to us while we say it. This act of the will "proves" to the priest that we are seeking reconciliation with God. The priest stands as a legal and sacramental witness to this repentance. If someone said, "I don't want to pray the Act of Contrition," then the priest would say, "I will not absolve you." As the Council of Trent teaches (Session 14), contrition is a necessary component of the sacrament of Penance. No sadness for sin, no grace.
Now this should reveal the absolutely important role of the Act of Contrition. It becomes the heartfelt prayer of the penitent to God. We list our sins to the priest as God's representative, but we make our act of contrition directly to God.
Here's the traditional Act of Contrition:
O my God, I am heartily sorry for having offended Thee, and I detest all my sins, because I dread the loss of heaven, and the pains of hell;
but most of all because they offend Thee, my God,
Who are all good and deserving of all my love.
I firmly resolve, with the help of Thy grace,
to sin no more and avoid the near occasions of sin. Amen.*
Now I used to make up a "custom" Act of Contrition some times in confession. However, a holy priest told me not to do this. I was shocked and I asked him why.
The holy priest explained that the more contrite we are, the more sanctifying grace we receive in the sacrament of Penance. Father also stated that a greater contrition remits more temporal punishment (crudely: remits more time off in purgatory). Most importantly, Father stated that most "custom Acts of Contrition" do not make explicit the essential elements of an Acts of Contrition. Such custom Acts of Contrition can be ambiguous and my not mention love of God or an the explicit intention to avoid sin and the occasion of sin "to sin no more."
The official Act of Contrition contains the necessary part of contrition stipulated by the Council of Trent, and so the words can excite in us the right and proper sentiments, thoughts, and most importantly, movement of the will toward God.
This, of course, does not forbid you making a "custom" Act of Contrition with all the right components. However, you might be flustered and forget it. Shoot, some of us still get flustered saying the traditional memorized version that we've been saying for years and years.
So as the holy priest said, if you want to make sure that you cover all the elements of contrition and that you excite your will to a true contrition with all the attending extra graces, use the Church's recommended Act of Contrition...that's they way all the saints did it.
PS: A great way to memorize the Act of Contrition (and have your children memorize it) is to begin the Rosary every evening with the Act of Contrition.
* An alternative version of the Act of Contrition substitutes "just judgments" for the "the loss of heaven and the pains of hell." As far as I can tell, the version above is more official. The version with "just judgments" usually appears in children's catechisms (e.g. Baltimore Catechism). Perhaps someone knows the origin of this difference. Please share it with us.